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Transglutaminase (EC 2.3.2.13, TGase), an enzyme that catalyzes the formation of covalent cross-links between protein or peptide molecules, plays a critical role in commercial food processing, medicine, and textiles. TGase from Streptomyces is the sole commercial enzyme preparation for cross-linking proteins. In this study, we revealed that the SOS response repressor protein LexA in Streptomyces mobaraensis not only triggers morphological development but also enhances TGase synthesis. The absence of lexA significantly diminished TGase production and sporulation. Although LexA does not bind directly to the promoter region of the TGase gene, it indirectly stimulates transcription of the tga gene, which encodes TGase. Furthermore, LexA directly enhances the expression of genes associated with protein synthesis and transcription factors, thus favorably influencing TGase synthesis at both the transcriptional and posttranscriptional levels. Moreover, LexA activates four crucial genes involved in morphological differentiation, promoting spore maturation. Overall, our findings suggest that LexA plays a dual role as a master regulator of the SOS response and a significant contributor to TGase regulation and certain aspects of secondary metabolism, offering insights into the cellular functions of LexA and facilitating the strategic engineering of TGase overproducers. [ABSTRACT FROM AUTHOR]

Copyright of China Condiment is the property of China Condiment and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The emulsions prepared by three non-meat proteins, sodium caseinate (SC), soy protein isolate (SPI) and egg white protein (EPI), were individually added to the continuous phase of myofibrillar protein (MP) sol to form MP composite gels to simulate meat products. The research aimed to investigate the effects of Transglutaminase (TGase) on the physicochemical properties, microstructure and water phase distribution of non-meat protein emulsion MP composite gels. The results of this study revealed that TGase played a crucial role in forming a tight gel network structure in the composite gels. This enhanced their ability to retain water and improved their overall gel strength. Additionally, TGase increased the gel formation temperature of myofibrillar proteins. Electrophoresis analysis showed that when catalyzed by TGase, there was a lighter band compared to those not catalyzed by TGase. This indicated that the addition of TGase facilitated cross-linking interactions between meat proteins and non-meat proteins in the composite gels. Furthermore, microscopy observations demonstrated that composite gels treated with TGase exhibited a more uniform microstructure. This could be attributed to an acceleration in relaxation time T2. The uniform network structure restricted the movement of water molecules in the gel matrix, thereby improving its water-holding capacity. Overall, these findings highlight how incorporating non-meat proteins into myofibrillar systems can be effectively achieved through enzymatic treatment with TGase. Such modifications not only enhanced important functional properties but also contributed towards developing alternative meat products with improved texture and moisture retention abilities. [ABSTRACT FROM AUTHOR]

Copyright of Modern Food Science & Technology is the property of Editorial Office of Modern Food Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Circulating uremic toxin indoxyl sulfate (IS), endothelial cell (EC) dysfunction, and decreased nitric oxide (NO) bioavailability are found in chronic kidney disease patients. NO nitrosylates/denitrosylates a specific protein's cysteine residue(s), forming S-nitrosothios (SNOs), and the decreased NO bioavailability could interfere with NO-mediated signaling events. We were interested in investigating the underlying mechanism(s) of the reduced NO and how it would regulate the S-nitrosylation of tissue transglutaminase (TG2) and its substrates on glycolytic, redox and inflammatory responses in normal and IS-induced EC injury. TG2, a therapeutic target for fibrosis, has a Ca2+-dependent transamidase (TGase) that is modulated by S-nitrosylation. We found IS increased oxidative stress, reduced NADPH and GSH levels, and uncoupled eNOS to generate NO. Immunoblot analysis demonstrated the upregulation of an angiotensin-converting enzyme (ACE) and significant downregulation of the beneficial ACE2 isoform that could contribute to oxidative stress in IS-induced injury. An in situ TGase assay demonstrated IS-activated TG2/TGase aminylated eNOS, NFkB, IkBα, PKM2, G6PD, GAPDH, and fibronectin (FN), leading to caspases activation. Except for FN, TGase substrates were all differentially S-nitrosylated either with or without IS but were denitrosylated in the presence of a specific, irreversible TG2/TGase inhibitor ZDON, suggesting ZDON-bound TG2 was not effectively transnitrosylating to TG2/TGase substrates. The data suggest novel roles of TG2 in the aminylation of its substrates and could also potentially function as a Cys-to-Cys S-nitrosylase to exert NO's bioactivity to its substrates and modulate glycolysis, redox, and inflammation in normal and IS-induced EC injury. [ABSTRACT FROM AUTHOR]

Lentinula edodes has high nutritional value and abundant protein. In order to develop and utilize edible mushroom protein, this study was designed to investigate the effects of TGase-catalyzed glycosylation and cross-linking on the physicochemical and functional properties of Lentinus edodes protein fraction. The results showed that within a certain time, glycosylation and TGase-catalyzed glycosylation decreased the total sulfydryl, free sulfydryl, disulfide bond, surface hydrophobicity, β-fold and α-helix, but increased the fluorescence intensity, random coil, β-turn, particle size and thermal stability. The apparent viscosity and the shear stress of the protein with an increase in shear rate were increased, indicating that TGase-catalyzed glycosylation promoted the generation of cross-linked polymers. In addition, the TGase-catalyzed glycosylated proteins showed a compact texture structure similar to the glycosylated proteins at the beginning, indicating that they formed a stable three-dimensional network structure. The flaky structure of proteins became more and more obvious with time. Moreover, the solubility, emulsification, stability and oil-holding capacity of enzymatic glycosylated Lentinus edodes protein fraction were significantly improved because of the proper TGase effects of glycosylation grafting and cross-linking. These results showed that glycosylation and TGase-catalyzed glycosylation could improve the processing characteristics of the Lentinula edodes protein fraction to varying degrees. [ABSTRACT FROM AUTHOR]

In highly intensive greenhouse vegetable production, soil acidification was caused by excessive fertilization, increasing cadmium (Cd) concentrations in the vegetables, which bears environmental hazards and is a negative influence on vegetables and humans. Transglutaminases (TGases), a central mediator for certain physiological effects of polyamines (PAs) in the plant kingdom, play important roles in plant development and stress response. Despite increased research on the crucial role of TGase in protecting against environmental stresses, relatively little is known about the mechanisms of Cd tolerance. In this study, we found, TGase activity and transcript level, which was upregulated by Cd, and TGase-induced Cd tolerance related to endogenous bound PAs increase and formation of nitric oxide (NO). Plant growth of tgase mutants was hypersensitive to Cd, chemical complementation by putrescine, sodium nitroprusside (SNP, nitric oxide donor) or gain of function TGase experiments restore Cd tolerance. α-diflouromethylornithine (DFMO, a selective ODC inhibitor) and 2–4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, NO scavenger), were respectively found declined drastically endogenous bound PA and NO content in TGase overexpression plants. Likewise, we reported that TGase interacted with polyamine uptake protein 3 (Put3), and the silencing of Put3 largely reduced TGase-induced Cd tolerance and bound PAs formation. This salvage strategy depends on TGase-regulated synthesis of bound PAs and NO that is able to positively increase the concentration of thiol and phytochelatins, elevate Cd in the cell wall, as well as induce the levels of expression Cd uptake and transport genes. Collectively, these findings indicate that TGase-mediated enhanced levels of bound PA and NO acts as a vital mechanism to protect the plant from Cd-caused toxicity.

This study aimed to evaluate the effects of high-voltage pulsed electric fields (HPEF) and transglutaminase (TGase) cross-clinking on the physicochemical and rheological properties of Pleurotus eryngii protein (PEP). The results showed that HPEF increased α-helixes and β-turns but decreased β-folds. A HPEF at 1500 V/cm maximized the free sulfhydryl content and solubility of PEP. TGase formed high-molecular-weight polymers in PEP. TGase at 0.25% maximized the free sulfhydryl groups, particle size, and solubility; shifted the maximum absorption wavelength from 343 nm to 339 nm and 341 nm; increased α-helixes and β-turns and decreased β-folds; and showed better rheological properties. Compared with TGase cross-linking, HPEF-1500 V/cm and 1% TGase significantly reduced the free sulfhydryl groups, particle size, and solubility, produced more uniform network structures, and improved the rheological properties. These results suggest that HPEF can increase the cross-linking of TGase and improve rheological properties of TGase-cross-linked PEP by affecting the physicochemical properties. [ABSTRACT FROM AUTHOR]

The emulsions prepared by three non-meat proteins, sodium caseinate (SC), soy protein isolate (SPI) and egg white protein (EPI), were individually added to the continuous phase of myofibrillar protein (MP) sol to form MP composite gels to simulate meat products. The research aimed to investigate the effects of Transglutaminase (TGase) on the physicochemical properties, microstructure and water phase distribution of non-meat protein emulsion MP composite gels. The results of this study revealed that TGase played a crucial role in forming a tight gel network structure in the composite gels. This enhanced their ability to retain water and improved their overall gel strength. Additionally, TGase increased the gel formation temperature of myofibrillar proteins. Electrophoresis analysis showed that when catalyzed by TGase, there was a lighter band compared to those not catalyzed by TGase. This indicated that the addition of TGase facilitated cross-linking interactions between meat proteins and non-meat proteins in the composite gels. Furthermore, microscopy observations demonstrated that composite gels treated with TGase exhibited a more uniform microstructure. This could be attributed to an acceleration in relaxation time T2. The uniform network structure restricted the movement of water molecules in the gel matrix, thereby improving its water-holding capacity. Overall, these findings highlight how incorporating non-meat proteins into myofibrillar systems can be effectively achieved through enzymatic treatment with TGase. Such modifications not only enhanced important functional properties but also contributed towards developing alternative meat products with improved texture and moisture retention abilities.

In this study, dopamine (DA) was used as the acyl receptor to modify zein through transglutaminase (TGase)-mediated reaction, producing self-adhesive zein (zein-DA complex). The structure of zein-DA complex was characterized by Fourier transform infrared spectrum (FT-IR), 1 H nuclear magnetic resonance spectrum ( 1 H NMR), and circular dichroism spectrum (CD), revealing the successful grafting of catechol structure of DA to zein. The results of SDS-PAGE demonstrated that zein-DA complex exhibited great ability of self-polymerization. The zein-DA complex absorbed on the cotton fabric surface imparted hydrophobicity with a water contact angle value (WCA) of 121.34 ± 1.14° to the fabrics. After 5 washing cycles, the WCA still remained 100.28 ± 4.83°, which indicated the fabrics obtained relatively durable hydrophobicity due to the self-adhesion of zein-DA complex. The results of FT-IR, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and color reaction tests manifested that much more protein attached on the surface of cotton fabric treated with zein-DA complex after washing compared with that with zein, which verified that the zein-DA complex had strong adhesion properties. Due to the introduction of DA, the relative DPPH free radical scavenging activity of cotton treated with zein-DA complex reached 43.60 ± 0.28 %, which was obviously higher than cotton treated with zein. The functionalized fabrics with zein-DA complex had both hydrophobicity and antioxidant activities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Circulating uremic toxin indoxyl sulfate (IS), endothelial cell (EC) dysfunction, and decreased nitric oxide (NO) bioavailability are found in chronic kidney disease patients. NO nitrosylates/denitrosylates a specific protein’s cysteine residue(s), forming S-nitrosothios (SNOs), and the decreased NO bioavailability could interfere with NO-mediated signaling events. We were interested in investigating the underlying mechanism(s) of the reduced NO and how it would regulate the S-nitrosylation of tissue transglutaminase (TG2) and its substrates on glycolytic, redox and inflammatory responses in normal and IS-induced EC injury. TG2, a therapeutic target for fibrosis, has a Ca2+-dependent transamidase (TGase) that is modulated by S-nitrosylation. We found IS increased oxidative stress, reduced NADPH and GSH levels, and uncoupled eNOS to generate NO. Immunoblot analysis demonstrated the upregulation of an angiotensin-converting enzyme (ACE) and significant downregulation of the beneficial ACE2 isoform that could contribute to oxidative stress in IS-induced injury. An in situ TGase assay demonstrated IS-activated TG2/TGase aminylated eNOS, NFkB, IkBα, PKM2, G6PD, GAPDH, and fibronectin (FN), leading to caspases activation. Except for FN, TGase substrates were all differentially S-nitrosylated either with or without IS but were denitrosylated in the presence of a specific, irreversible TG2/TGase inhibitor ZDON, suggesting ZDON-bound TG2 was not effectively transnitrosylating to TG2/TGase substrates. The data suggest novel roles of TG2 in the aminylation of its substrates and could also potentially function as a Cys-to-Cys S-nitrosylase to exert NO’s bioactivity to its substrates and modulate glycolysis, redox, and inflammation in normal and IS-induced EC injury.

Down fiber – a natural and environmentally recyclable insulation material – is applied mainly in the area of natural-filled products. However, owing to its natural deficiencies of low fluffiness and thermal stability, large-scale application is limited. In our work, an enzyme preparation (transglutaminase (TGase)) was used as a fluffy agent to improve the fluffy degree of down. With fluffy as the main index, the single factor condition of only using TGase enzyme was optimized, and fluffiness was increased by 22%. On the basis of this optimum condition, the compound dosage of papain and TGase was further optimized. The fluffy degree of down was improved by hydrolysis of papain and crosslinking of TGase. Amino group content, thermogravimetry (TG), differential scanning calorimetry (DSC), moisture absorption, tensile strength, and elongation at break of down treated with different enzyme reagents were tested. The results showed that the thermal stability of down fiber treated with the multi enzyme increased significantly, the denaturation temperature was increased from 53.7°C to 77.4°C, and the moisture absorption was also improved. The elastic property also exhibited a great enhancement; elongation at break increased from 12.4% to 37.7%, nearly three times higher than the original property, and the tensile strength increased from 180 MPa to 370 MPa, almost 2.1 times as much as before, increased by 105.6%. [ABSTRACT FROM AUTHOR]

Copyright of Storage & Process is the property of Tianjin Academy of Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lentinula edodes has high nutritional value and abundant protein. In order to develop and utilize edible mushroom protein, this study was designed to investigate the effects of TGase-catalyzed glycosylation and cross-linking on the physicochemical and functional properties of Lentinus edodes protein fraction. The results showed that within a certain time, glycosylation and TGase-catalyzed glycosylation decreased the total sulfydryl, free sulfydryl, disulfide bond, surface hydrophobicity, β-fold and α-helix, but increased the fluorescence intensity, random coil, β-turn, particle size and thermal stability. The apparent viscosity and the shear stress of the protein with an increase in shear rate were increased, indicating that TGase-catalyzed glycosylation promoted the generation of cross-linked polymers. In addition, the TGase-catalyzed glycosylated proteins showed a compact texture structure similar to the glycosylated proteins at the beginning, indicating that they formed a stable three-dimensional network structure. The flaky structure of proteins became more and more obvious with time. Moreover, the solubility, emulsification, stability and oil-holding capacity of enzymatic glycosylated Lentinus edodes protein fraction were significantly improved because of the proper TGase effects of glycosylation grafting and cross-linking. These results showed that glycosylation and TGase-catalyzed glycosylation could improve the processing characteristics of the Lentinula edodes protein fraction to varying degrees.

This study aimed to evaluate the effects of high-voltage pulsed electric fields (HPEF) and transglutaminase (TGase) cross-clinking on the physicochemical and rheological properties of Pleurotus eryngii protein (PEP). The results showed that HPEF increased α-helixes and β-turns but decreased β-folds. A HPEF at 1500 V/cm maximized the free sulfhydryl content and solubility of PEP. TGase formed high-molecular-weight polymers in PEP. TGase at 0.25% maximized the free sulfhydryl groups, particle size, and solubility; shifted the maximum absorption wavelength from 343 nm to 339 nm and 341 nm; increased α-helixes and β-turns and decreased β-folds; and showed better rheological properties. Compared with TGase cross-linking, HPEF-1500 V/cm and 1% TGase significantly reduced the free sulfhydryl groups, particle size, and solubility, produced more uniform network structures, and improved the rheological properties. These results suggest that HPEF can increase the cross-linking of TGase and improve rheological properties of TGase-cross-linked PEP by affecting the physicochemical properties.

Gelatin is a peptide molecule polymer produced by moderate hydrolysis of collagen, and it has been widely used in food and medicine, among many other fields. In this paper, fish gelatin was modified by tannic acid and transglutaminase (TGase), and their effects on the gelation strength of fish gelatin were discussed. The concentration of gelatin, the oxidized and non-oxidized tannic acid, and the treatment conditions of TGase were optimized respectively to measure the change of gelation strength, and the optimal combination of tannic acid and TGase was obtained. With the addition of 1U • g-1 TGase and 0.2 % (V/ V) of (2 % m/ V) oxidized tannic acid at 6% gelatin concentration, the gel strength of fish gelatin reached 946.2g. Tannie acid and TGase can synergistically enhance the strength of fish gelatin. This study will reduce the amount of gelatin per unit, reduce the use cost of fish gelatin, and expand its application range. [ABSTRACT FROM AUTHOR]

In the present study, the effect of transglutaminase (TGase) concentration on the physical and oxidative stabilities of filled hydrogel particles created by biopolymer phase separation was investigated. The results showed that filled hydrogels had relatively smaller particle sizes, higher absolute zeta-potentials, higher interfacial layer thicknesses and lightness values with the increasing of TGase concentration (P < 0.05), as evidenced by the apparent viscosity and viscoelasticity behavior. However, the relatively higher TGase concentration promoted the protein aggregation, which weakens the protection of the surface protein layer, having the negatively impacted the physical stability of filled hydrogels. Microstructural images which obtained via cryo-scanning electron microscopy also verified the above results. In particular, it is noted that filled hydrogels displayed the lowest degrees of lipid and protein oxidation during 10 days of storage (P < 0.05) at TGase concentration of 10 U/g. Prevention against oxidation was attributed mainly to TGase crosslinking of protein molecules on the surface of droplets, which likely provided a denser interface around lipid droplets. Our results indicated that TGase was a favourable agent to crosslink protein on the surface of lipid and improve the physical and oxidative stability of filled hydrogel particles. [ABSTRACT FROM AUTHOR]

Rice bran (RB) is a good source of dietary fibre. Addition of rice bran into croissant interferes with the gluten formation of dough and hence affect the physicochemical properties of croissant. The effect of RB addition on physicochemical properties of croissant were determined by using 0%, 10% and 15% RB. Besides, additives such as emulsifiers and enzymes can be used in pastry to enhance the physicochemical properties of croissant. Diacetyl tartaric acid ester of mono-diglycerides (DATEM) and transglutaminase (TGase) were used respectively on 0%, 10% and 15% RB to investigate the effect of such additives on physicochemical properties of croissant. Increased % RB and DATEM, produced a significant decrease in specific volume, together with a significant increase in colour, hardness and chewiness. With increased % RB, TGase caused significant increase in colour, hardness and chewiness but significant decrease in specific volume. The overall moisture sorption isotherm curves of the croissant belong to the Type III isotherm, also known as Flory-Huggins Isotherm (J-shaped). The critical aw obtained from the Guggenheim-Anderson-de Boer (GAB) equation showed that the shelf life of croissants were not positively impacted by the addition of DATEM and TGase and the addition of RB did not cause any significant positive effects on quality characteristics of croissants.

Transglutaminase (EC 2.3.2.13, TGase), an enzyme that catalyzes the formation of covalent cross-links between protein or peptide molecules, plays a critical role in commercial food processing, medicine, and textiles. TGase from Streptomyces is the sole commercial enzyme preparation for cross-linking proteins. In this study, we revealed that the SOS response repressor protein LexA in Streptomyces mobaraensis not only triggers morphological development but also enhances TGase synthesis. The absence of lexA significantly diminished TGase production and sporulation. Although LexA does not bind directly to the promoter region of the TGase gene, it indirectly stimulates transcription of the tga gene, which encodes TGase. Furthermore, LexA directly enhances the expression of genes associated with protein synthesis and transcription factors, thus favorably influencing TGase synthesis at both the transcriptional and posttranscriptional levels. Moreover, LexA activates four crucial genes involved in morphological differentiation, promoting spore maturation. Overall, our findings suggest that LexA plays a dual role as a master regulator of the SOS response and a significant contributor to TGase regulation and certain aspects of secondary metabolism, offering insights into the cellular functions of LexA and facilitating the strategic engineering of TGase overproducers., Competing Interests: FY and GL were employed by Jiangsu Yiming Biological Technology Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer LB declared a past co-authorship with the author WW to the handling editor., (Copyright © 2024 Shi, Yan, Yuan, Li, Liu, Li, Yu, Li, Zhu and Wang.)

Transglutaminase (TGase) is inextricably associated with plant growth and development. However, the mechanism by which TGase enhances salt tolerance of higher plants under salt stress is poorly understood. In this study, we investigated the effects of NaCl stress and exogenous o-phenanthroline (o-Phen, a metalloprotease inhibitor) on TGase activity, chlorophyll fluorescence parameters, carbohydrates contents, the reactive oxygen species (ROS) scavenging system, and endogenous polyamines (PAs) contents of salt-sensitive 'Jinyou No. 4′ and salt-tolerant 'Inbred Line 9930' cucumber. Salt stress significantly inhibited plant growth of the two cultivars, as well as hindered carbohydrates transport, which was more evident in the salt-sensitive cultivar. TGase activity and expression, ROS scavenging capacity, and bound PAs content were up-regulated by salt stress to some extent, which was more distinct in the salt-tolerant cucumber cultivar. However, o-Phen treatment significantly inhibited TGase expression, and further decreased plant growth and the actual photochemical efficiency of photosystem II in the two cultivars. In addition, application of o-Phen significantly decreased endogenous PAs content in leaves of 'Jinyou No. 4' and 'Inbred Line 9930' seedlings by 9.60% and 42.32% under NaCl stress, respectively. These results suggested that high activity of TGase increases the salt stress tolerance of cucumber plants by increasing endogenous PAs content and ROS scavenging capacity, and promoting carbon assimilation and photosynthetic products. • Salt stress caused plant growth retardation as well as inhibited transportation of carbohydrates both in the two cucumber cultivars. • Salt tolerant cucumber variety showed higher transglutaminase (TGase) activity as well as increasing bound polyamines (PAs) content and reactive oxygen scavenging capacity. • o-Phen treatment reduced accumulation of bound PAs. • The o-Phen treatment reduced photochemical efficiency of PSII of the two cucumber cultivars. [ABSTRACT FROM AUTHOR]

Highlights • TGase enhanced the gel strength and water holding capacity of high-fiber tofu. • TGase alleviated the viscoelasticity loss of tofu gel induced by okara. • AB and A 1,2,4 subunits were more prone to aggregate during the heating of soymilk. • TGase-induced ε-(γ-glutamyl) lysine of strengthened the network of high-fiber tofu. • TGase promoted the ordered formation of protein aggregates and could wrap okara. Abstract Introducing okara to develop high-fiber tofu (HFT) can effectively increase the utilization of soy residues as well as enhance the nutrition of tofu. However, okara degrades the glucono-δ-lactone (GDL)-induced tofu quality. Current results showed that microbial transglutaminase (TGase) remarkably enhanced the gel strength, water holding capacity and viscoelasticity of HFT. During heating of soymilk, AB and A 1,2,4 subunits of 11S were more prone to aggregate via disulfide (SS) bonds to form larger soluble protein aggregates under neutral condition, while the SS-mediated insoluble aggregates were formed under acid condition by GDL and predominantly contributed to the structure of tofu without TGase. TGase-induced intermolecular ε-(γ-glutamyl) lysine strengthened protein network and contributed the most to HFT structure. TGase promoted formation of protein aggregates more orderly, and okara was well-wrapped by protein network. These results demonstrated that the macro-protein aggregates crosslinked by TGase conspicuously strengthened the gel network and significantly elevated the HFT quality. [ABSTRACT FROM AUTHOR]

Highlights • The digestion of surimi gels fit the Logistic equation (x = M x 0 x 0 + M - x 0 e - k M t ) well. • The digestibility of surimi gels without TGase decreased gradually. • The digestibility of surimi gels with TGase increased at first and then decreased. Abstract To explore the mechanism of gastric digestion of surimi gels induced by different adding amount of transglutaminase (TGase), the structures and gastric digestion of surimi gels were studied. With adding amount of TGase increasing, the crosslinking degree of surimi gels increased, the surface hydrophobicity reduced progressively, and high molecular polymers formed. The relationship between content of free amino acids and digestion time of surimi gels showed an S-shaped curve and could fit the Logistic equation (x = M x 0 x 0 + M - x 0 e - k M t ) well (R2 = 0.957–0.998). There were two digestion modes of surimi gels induced by different amounts of TGase. The time that reached to the maximum digestibility was prolonged with the increase of TGase adding amount. The results suggested that adding proper amount TGase to surimi was conducive to sustained release of nutrients and a theoretical foundation of surimi gels gastric digestion was built for surimi industry. [ABSTRACT FROM AUTHOR]

Hemocyanin is the main component of hemolymph plasma proteins and possesses diverse immunological properties and immunomodulatory functions. However, the interacting networks of hemocyanin in shrimp immune response remain poorly understood. In this study, 39 potential hemocyanin interacting partners were identified from Litopenaeus vannamei plasma by co-immunoprecipitation (Co-IP) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Gene Ontology (GO) analysis showed that most of the identified interactors were cell proteins involved in metabolic process and binding. Among these identified proteins, transglutaminase (TGase), a crucial regulator in hemolymph clotting cascade, was chosen for further studies. Far-Western blot and His-pull down assays revealed that hemocyanin directly interacted with TGase. Further analysis demonstrated that hemocyanin and TGase followed similar expression patterns upon pathogen infection. Moreover, in vivo knockdown of hemocyanin led to a significant decrease in TGase expression, as well as inhibited hemolymph clotting. Taken together, these data suggest that hemocyanin might positively regulate hemolymph clotting by modulating TGase in shrimp. The interaction networks among immune-related factors is critical for the innate immune response in invertebrates. We report for the first time, proteins that potentially interact with hemocyanin, which led to the identification of 39 possible hemocyanin-proteins including the clotting-related factor TGase. Further studies demonstrated that hemocyanin directly interacted with TGase and modulated its expression, therefore affecting the formation of hemolymph clotting. These findings not only extend our knowledge of the immune interaction networks but also contribute to shrimp disease control and prevention. Unlabelled Image • We identified 39 potential interacting partners in Litopenaeus vannamei plasma. • Hemocyanin was demonstrated to directly interact with TGase. • Hemocyanin could modulate TGase expression and affect the formation of hemolymph clotting. [ABSTRACT FROM AUTHOR]

In this study, we used two cucumber ( Cucumis sativus L.) cultivars with different salt tolerances, Jinyou NO.4 (salt-sensitive) and Inbred line 9930 (salt-tolerant), to investigate the effects of salt stress (75 mM of NaCl) on photosynthesis and antioxidant capacity in cucumber leaves. The results showed that the plant height, fresh weight, and dry weight of the seedlings from the two cultivars were decreased under salt stress. The restrained degree of growth parameters induced by NaCl was more serious in Jinyou NO.4 than in Inbred line 9930. Salt stress caused significant decreases in photosynthetic pigment content, chl a / b , Pn, Gs and Tr in the leaves of the two cultivars. Ci content was increased in Jinyou NO.4, and it was decreased in Inbred line 9930. Moreover, Fv/Fm, ΦPSII, qP, NPQ, and the mRNA expression levels of RbcL , RbcS and RCA were decreased in the two cucumber leaves under salt stress, and the effects of salt stress on Jinyou NO.4 were more serious. Meanwhile, the activities and encoding gene expression levels of SOD, POD, CAT, and APX were increased before being decreased under salt stress. These expression levels were greater in Inbred line 9930 than in Jinyou NO.4. NaCl stress-induced TGase activity, gene expression and bound PAs contents were higher in Inbred line 9930. Salt stress increased the MDA content and O 2 ∙－ generation rate in cucumber leaves, especially in Jinyou NO.4. These results suggested that salt-tolerant cultivars could enhance salinity tolerance by regulating photosynthetic efficiency and antioxidant capacity compared with the salt-sensitive cultivar. This could alleviate salt damage to cucumber seedlings. [ABSTRACT FROM AUTHOR]

In highly intensive greenhouse vegetable production, soil acidification was caused by excessive fertilization, increasing cadmium (Cd) concentrations in the vegetables, which bears environmental hazards and is a negative influence on vegetables and humans. Transglutaminases (TGases), a central mediator for certain physiological effects of polyamines (PAs) in the plant kingdom, play important roles in plant development and stress response. Despite increased research on the crucial role of TGase in protecting against environmental stresses, relatively little is known about the mechanisms of Cd tolerance. In this study, we found, TGase activity and transcript level, which was upregulated by Cd, and TGase-induced Cd tolerance related to endogenous bound PAs increase and formation of nitric oxide (NO). Plant growth of tgase mutants was hypersensitive to Cd, chemical complementation by putrescine, sodium nitroprusside (SNP, nitric oxide donor) or gain of function TGase experiments restore Cd tolerance. α-diflouromethylornithine (DFMO, a selective ODC inhibitor) and 2–4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO, NO scavenger), were respectively found declined drastically endogenous bound PA and NO content in TGase overexpression plants. Likewise, we reported that TGase interacted with polyamine uptake protein 3 (Put3), and the silencing of Put3 largely reduced TGase-induced Cd tolerance and bound PAs formation. This salvage strategy depends on TGase-regulated synthesis of bound PAs and NO that is able to positively increase the concentration of thiol and phytochelatins, elevate Cd in the cell wall, as well as induce the levels of expression Cd uptake and transport genes. Collectively, these findings indicate that TGase-mediated enhanced levels of bound PA and NO acts as a vital mechanism to protect the plant from Cd-caused toxicity. • TGase plays a critical role in Cd stress. • TGase increases higher accumulation of bound PAs, NO, GSH and PCs. • TGase enhances Cd tolerance by regulating Cd fixation in cell walls, Cd uptake, accumulation and transport. [ABSTRACT FROM AUTHOR]

Transglutaminase (TGase) is a regulator of posttranslational modification of protein that provides physiological protection against diverse environmental stresses in plants. Nonetheless, the mechanisms of TGase-mediated salt tolerance remain largely unknown. Here, we found that the transcription of cucumber TGase (CsTGase) was induced in response to light and during leaf development, and the CsTGase protein was expressed in the chloroplast and the cell wall. The overexpression of the CsTGase gene effectively ameliorated salt-induced photoinhibition in tobacco plants, increased the levels of chloroplast polyamines (PAs) and enhanced the abundance of D1 and D2 proteins. TGase also induced the expression of photosynthesis related genes and remodeling of thylakoids under normal conditions. However, salt stress treatment reduced the photosynthesis rate, PSII and PSI related genes expression, D1 and D2 proteins in wild-type (WT) plants, while these effects were alleviated in CsTGase overexpression plants. Taken together, our results indicate that TGase-dependent PA signaling protects the proteins of thylakoids, which plays a critical role in plant response to salt stress. Thus, overexpression of TGase may be an effective strategy for enhancing resistance to salt stress of salt-sensitive crops in agricultural production.

In this study, the combined effect of ultrasound pretreatment (US) and microbial transglutaminase (MTG) on the rheological, textural, and functional attributes of whey protein concentrate (WPC) were investigated. All the samples exhibited non-Newtonian shear-thinning behavior. Treatment with US lead to a significant increase in foaming capacity, gel hardness, and adhesiveness at 7.5 min, while reduced emulsifying capacity and syneresis at all levels. Moreover, consistency coefficient, foam stability, emulsifying capacity, emulsion stability, gel hardness and adhesiveness improved, whereas a slight decrease was observed in foaming capacity and syneresis of gels as a consequence of TG treatment respectively. 5 min US - 5 U·g − 1 pr TG treated sample exhibited the least syneresis value of all samples. SEM images affirmed the beneficial effects of treatments on texture, reduction of voids size and supported the textural results. Overall, ongoing US pretreatment and TG treatment were successful in modifying the functional properties of whey proteins. Industrial relevance Food industry is consuming whey proteins for their functional characteristics besides their nutritional value. Microbial transglutaminase (MTG) can modify whey protein structure. High intensity ultrasound (HIU) is also mentioned as a material-altering technology. Heat denaturation is used for changing whey protein structure before enzyme treatment. The purpose of this study was to investigate the feasibility of replacing heat denaturation by ultrasound treatment before transglutaminase addition to a whey protein system. We also aimed to test the simultaneous effect of US and TG in order to meet emerging demands and produce different novel targeted products. Our results indicated that US treatment may replace heat denaturation before TG treatment and combination of these two factors improved various properties of whey protein systems. [ABSTRACT FROM AUTHOR]

Functional and bioactive properties of crayfish meat convert their surpluses in an excellent alternative for the development of food products. Thus, protein dispersions were subjected to a thermal treatment, obtaining a protein-based gel. Rheological and antioxidant properties were studied at three different pH values (2.0, 6.5 and 8.0) when the TGase enzyme was used. The pH value exerted a strong influence on the gelation behaviour, as well as on the functional properties and the antioxidant activity of the final gels. The activity of the TGase enzyme is highly influenced by the pH of the protein dispersions. The highest antioxidant activity was obtained against ABTS and the lowest when FC reagent was used, whereas the activity against DPPH was also remarkable. TGase enzyme can be used during the thermal treatment to increase the mechanical properties, which were lost when hydrolysate systems were used. [ABSTRACT FROM AUTHOR]

Transglutaminase (TGase) and succinylation could modify the physicochemical characteristics and the functional properties of proteins. The aim of this work was to cross-link egg white protein (EWP) and succinylated casein with TGase and to assess the feasibility of making a novel composite protein film. The effects of succinylated casein content, reaction time, and TGase concentration on the mechanical properties, physical characteristics (thermal property and degree of crystallinity), and structure properties (secondary structure and surface micrograph structure) of the film were investigated in this study. The results revealed that the susceptibility of EWP to TGase-mediated cross-linking modification was enhanced by succinylated casein. Meanwhile, the films with TGase were more homogeneous and smoother and possessed better water resistance and thermal stability. The content of α-helix, β-turn structures were increased whereas β-sheet structure was decreased. The spatial conformation and degree of crystallinity of composite protein film were also affected by TGase. The increase of the degree of crystallinity of the composite film further proved the improvement of film mechanical properties induced by TGase and succinylated casein. Based on the above results, this study provides relevant data and insights for the TGase/chemical modification of protein-based edible films. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of NaCl and TGase on the gelling properties and structures of heat-induced arachin and basil seed gum composite gels. It was found that the combination of NaCl and TGase significantly enhanced the gel strength, storage modulus, and water holding capacity of the composite gels, which was superior to those of the gels only added with NaCl or TGase. The low field nuclear magnetic resonance (LF-NMR) results showed that the addition of NaCl and TGase decreased the T 21 and T 22 relaxation time due to the formation of compact gel network. The gel added with NaCl first and then crosslinked by TGase showed a denser microstructure and a higher freeze-thaw stability. Moreover, the secondary structures of arachin and the color of the composite gels could be significantly influenced by the addition order of NaCl and TGase. These results may provide some useful information for designing gel foods with various textural and sensory characteristics. [Display omitted] • The structures of arachin-BSG composite gels were greatly changed by TGase. • TGase improved the gelling properties of Ara-BSG gels more effectively than NaCl. • The addition of NaCl first could facilitate the cross-linking of arachin by TGase. • The combination of NaCl and TGase endowed the gel with a more compact network. • The addition order of NaCl and TGase can regulate the gelling properties. [ABSTRACT FROM AUTHOR]

The functional properties (elasticity and water holding capacity) of soy protein isolate (SPI) are degraded by denaturalization during frozen storage. To solve this problem, a modified SPI was prepared by cross-linking SPI and gelatin with transglutanminase (TGase). The gel properties of the modified SPI were analyzed during frozen storage. After 20 days of frozen storage, the water holding capacity (WHC) of the SPI gels decreased from 89% to 65%, whereas that of the modified soybean protein isolate (MSPI) gels remained above 85%, which was 29.6% higher than that of the SPI gels. In addition, the hardness increment of the MSPI gels only accounted for 47.1% that of the SPI gels. The moisture distribution of the MSPI gels showed no significant change during frozen storage, and the content of unfreezing water in the MSPI gels was higher than that in the SPI gels. Confocal laser scanning microscopy revealed that the microstructure of the MSPI gels suffered minimal damage after frozen storage, whereas that of the SPI gels presented a honeycomb pattern after frozen storage. Analysis of soluble protein, total SH groups, and gel chemical interaction showed that the improvement of MSPI gel properties during frozen storage was due to the slight decrease in the amount of gel soluble proteins and total SH groups and to the chemical interaction among different gels. [ABSTRACT FROM AUTHOR]

In this study surimi was produced from big head (Hypophtalmichthys nobilis) carp and the effects of three independent factors including microbial transglutaminase (0.5%, 0.75% and 1%), salt (0%, 1.25% and 2.5%) and temperature (35oC, 40oC and 45oC), were examined on textural properties and color parameters of produced surimi was examined. The results showed that enzyme concentration of 0.5 % and 1.25% of salt at 45oC temperature were as optimum treatment, thereby, reducing the salt percentage from 2.5% to 1.25% without significant reduction in textural properties such as Hardness (resistance of food at the first bitting of the food), Cohesiveness (maintaining the strength of the food during chewing) and Springiness (ability of foos to recovery of its origin shape and size at the first biting). The increasing of the amount of enzyme also resulted in reduction of WHC, significantly (p<0.05). Moreover, when the enzyme and salt were used at low concentrations, the more whiteness and lightness of surimi gel wre produced. Simultaneous effect of salt increasing and setting temperature reduction, resulted in significant higher redness (a*) (p<0.05). Besides, the effect of enzyme alone on yellow factor (b*) was not significant, whereas the simultaneous effect of increasing in enzyme and temperature resulted higher b* factor (p<0.05). [ABSTRACT FROM AUTHOR]

[Display omitted] • Structure-properties were associated to the covalent cross-linking degree. • Covalent cross-linking altered the inherent molecular structure of gelatin gel. • Intra-molecular and inter-molecular cross-linking had different reactivity at different crosslinking degrees. • Intra-molecular cross-linking was more conducive to the improvement of gelatin hardness. In this work, the structure–property differences and mechanisms of gelatin induced by transglutaminase (TGase) covalent cross-linking were investigated. The results showed that higher hardness was obtained with a cross-linking degree of 13.55%, attributing to an active intra-molecular cross-linking and a tight network structure under a certain amount of triple helix-like structure. The inter-molecular cross-linking played a positive role in the transition from random coil to left-handed single helix chains, while triple helix-like structure could not been formed owing to the steric hindrance and hydrogen bond reduction, showing the decrease of hardness and increase of viscosity. Additionally, the ε-(γ-Glu)-Lys isopeptide bond significantly increased the initial degradation temperature. Macromolecular polymers with a cross-linking degree of 37.48% allowed sol state of gelatin gel could be maintained even heating at 100 ℃ for 10 min. This study might provide an innovative reference for the regulation and application of gelatin gel structure-properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • TGase and PCB2 synergistically improved the antioxidant capacity and texture properties of MP. • TGase and PCB2 increase the compactness and water holding capacity of three-dimensional network structure of MP gel. • XRD, for the first time, detects the structure changes of MP. We investigated the roles of Proanthocyanidin B2 (PCB2) and transglutaminase (TGase) in improving myofibrillar protein (MP) gel properties. TGase and PCB2 increased the surface hydrophobicity (41 %) and water holding capacity (WHC) (16 %) of the MP. Secondary and tertiary structures of MP were respectively analyzed by Fourier transform infrared spectroscopy (FTIR) and fluorescence spectrophotometry. The content of α -helix in MP was found to be increased while its fluorescence intensity decreased upon the addition of PCB2 and TGase. The addition of PCB2 and TGase resulted in formation of a dense MP network structure as revealed by scanning electron microscopy (SEM). Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) analysis showed that immobilized water levels in the MP gel were markedly increased while the amount of free water was significantly decreased after PCB2 and TGase addition. These findings indicate that a combination of PCB2 and TGase are potential additives for meat products. [ABSTRACT FROM AUTHOR]

Streptomyces is well known to be an attractive host for producing large amounts of proteins with potent biological activities into the culture supernatant. To expand its expression system, we constructed a novel expression plasmid for gene expression in Streptomyces by inserting the promoter (P tg ) and the signal peptide (SP tg ) of transglutaminase (TGase) from Streptomyces hygroscopicus WSH03-13 into vector pIJ86, followed by multiple cloning sites and a transcriptional terminator fd (fd-ter). The secretion capacity of the vector was further enhanced by optimizing the signal peptidase cleavage site and a rare codon of SP tg , yielding expression vector pSG02. Using this vector, TGase was actively and greatly expressed in the supernatant in several Streptomyces strains. In addition, the heterologous proteins aminopeptidase from Bacillus subtilis Zj016 (BSAP) and phenylalanine ammonia-lyase from Rhodotorula glutinis (PAL) were also expressed in various Streptomyces strains by this vector. This expression system should be useful for the expression of other proteins. [ABSTRACT FROM AUTHOR]

Abstract: Incorporating exogenous proteins into food production is a common practice for improving processing characteristics. In the present study, oat dough containing 15% (w/w, blends of protein-oat flour basis [POB]) vital wheat gluten (VWG) or 15% (w/w, POB) egg albumin (EA) was used to produce noodles with or without gluten (i.e., gluten-free). The rheological and noodle-making characteristics of oat dough containing exogenous proteins and the effects of added transglutaminase (TGase) were examined. The results indicate that the extent of TGase’s modification of the thermomechanical and dynamic rheological characteristics (G′ and G″) is dependent on the source of exogenous proteins in the oat dough. By adding 1.0% (w/w, POB) TGase, the cooking qualities of the resulting noodles (i.e., those containing VWG and EA) were significantly elevated with lower cooking loss; the elasticity of both types of noodles increased. The effects of TGase in different dough systems were analyzed by SDS–PAGE. In oat dough prepared with VWG, TGase was shown to catalyse the cross-linking of both oat protein and gluten protein; however, oat protein acted as the only substrate of TGase in the noodles that had been prepared with EA. [Copyright &y& Elsevier]

[Display omitted] • The location of lysine involved in TGase-induced cross-linking was identified. • The number of cross-linking sites increased with the cross-linking degree. • The main cross-linking domain moved from the head to rod with cross-linking degree. Surimi gels with different cross-linking degrees (18.52%, 34.67%, 62.87% and 79.11%) were prepared to identify the numbers and locations of lysine residues involved in TGase-induced cross-linking, and to reveal the quantity and location relationships among cross-linking degrees, cross-linking sites and digestion sites by using trypsin digestion, SDS-PAGE and LC-MS/MS methods. The results showed that with the increase in cross-linking degree from 18.52% to 79.11%, 1) the quantity of cross-linking sites gradually increased from 25 sites to 47 sites, 2) the main possible cross-linking domain moved from myosin head to rod, 3) the numbers of digestion sites first decreased from 1262 sites to 1194 sites, and then increased to 1302 sites, 4) the changes in the values of digestion sites were mainly concentrated in myosin rod and it was also the main region of digestion. This study can help exploring the relationship between enzymatic cross-linking and nutritional properties of food. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the involvement of oxidative stress in glutamate-evoked transglutaminase (TGase) upregulation in astrocyte cultures (14 DIV). A 24 h exposure to glutamate caused a dose-dependent depletion of glutathione intracellular content and increased the ROS production in cell cultures. These effects were receptor-mediated, as demonstrated by inhibition with GYKI 52466. The pre-incubation with glutathione ethyl ester or cysteamine recovered oxidative status and was effective in significantly reducing glutamate-increased tissue TGase. These data suggest that tissue TGase upregulation may be part of a biochemical response to oxidative stress induced by a prolonged exposure of astrocyte cultures to glutamate. [Copyright &y& Elsevier]

Transglutaminases (TGases) catalyze the cross-linking of peptides and proteins by the formation of γ-glutamyl-ε-lysyl bonds. Given the implication of tissue TGase in various physiological disorders, development of specific tissue TGase inhibitors is of current interest. To aid in the design of peptide-based inhibitors, a better understanding of the mode of binding of model peptide substrates to the enzyme is required. Using a combined kinetic/molecular modeling approach, we have generated a model for the binding of small acyl-donor peptide substrates to tissue TGase from red sea bream. Kinetic analysis of various N-terminally derivatized Gln-Xaa peptides has demonstrated that many CBz-Gln-Xaa peptides are typical in vitro substrates with KM values between 1.9 mM and 9.4 mM, whereas Boc-Gln-Gly is not a substrate, demonstrating the importance of the CBz group for recognition. Our binding model of CBz-Gln-Gly on tissue TGase has allowed us to propose the following steps in the acylation of tissue TGase. First, the active site is opened by displacement of conserved W329. Second, the substrate Gln side chain enters the active site and is stabilized by hydrophobic interaction with conserved residue W236. Third, a hydrogen bond network is formed between the substrate Gln side chain and conserved residues Y515 and the acid-base catalyst H332 that helps to orient and activate the γ-carboxamide group for nucleophilic attack by the catalytic sulphur atom. Finally, an H-bond with Y515 stabilizes the oxyanion formed during the reaction. [ABSTRACT FROM AUTHOR]

The epidermis of vertebrates forms an extended organ to protect and exchange gas, water, and organic molecules with aquatic and terrestrial environments. Herein, the processes of keratinization and cornification in aquatic and terrestrial vertebrates were compared using immunohistochemistry. Keratins with low cysteine and glycine contents form the main bulk of proteins in the anamniote epidermis, which undergoes keratinization. In contrast, specialized keratins rich in cysteine-glycine and keratin associated corneous proteins rich in cysteine, glycine, and tyrosine form the bulk of proteins of amniote soft cornification in the epidermis and hard cornification in scales, claws, beak, feathers, hairs, and horns. Transglutaminase (TGase) and sulfhydryl oxidase (SOXase) are the main enzymes involved in cornification. Their evolution was fundamental for the terrestrial adaptation of vertebrates. Immunohistochemistry results revealed that TGase and SOXase were low to absent in fish and amphibian epidermis, while they increased in the epidermis of amniotes with the evolution of the stratum corneum and skin appendages. TGase aids the formation of isopeptide bonds, while SOXase forms disulfide bonds that generate numerous cross-links between keratins and associated corneous proteins, likely increasing the mechanical resistance and durability of the amniote epidermis and its appendages. TGase is low to absent in the beta-corneous layers of sauropsids but is detected in the softer but pliable alpha-layers of sauropsids, mammalian epidermis, medulla, and inner root sheath of hairs. SOXase is present in hard and soft corneous appendages of reptiles, birds, and mammals, and determines cross-linking among corneous proteins of scales, claws, beaks, hairs, and feathers., (© 2021 American Association for Anatomy.)

Transglutaminases, calcium-dependent thiol enzymes, may be involved in cellular growth control and differentiation, having an intracellular regulatory role in some post-traslational modifications found in various classes of proteins. In order to elucidate the involvement of this class of enzymes in cellular differentiation processes, we have assayed transglutaminase activity in primary and subcultured rat glial cells. Reduced activity was found from 3rd to 5th passage. In the 5th passage the activity was some 50% of that found in the primary cultures and was not restored by addition of 10 μM retinoic acid. The decrease of TGase activity, observed during serial passages, could represent an early metabolic alteration related to cell dedifferentiation and loss of growth control. In fact, the subcultured cells may have undergone a 'disarranged' state, as confirmed by a decrease in GFAP-stained cells and glutamine synthetase activity, respectively, immunocytochemical and biochemical markers of astroglial cells. [ABSTRACT FROM AUTHOR]

• EGCG and TGase had a double-crosslinking effect on gel of myofibrillar proteins. • Molecular docking revealed covalent and non-covalent bond between EGCG and myosin. • Molecular docking confirmed catalytic mechanism of TGase using myosin as substrate. The aim of this study was to determine the influence and mechanism of combining EGCG with TGase on properties of myofibrillar protein (MP) gel. A double-crosslinked effect was observed when EGCG and TGase were added into MP gel. Breaking force, deformation, water holding capacity and hardness of double-crosslinked MP gel increased by 25.3 ± 3.0 g, 0.5 ± 0.3 mm, 1.76 ± 0.4% and 34.11 ± 2.56 g, compared with those of TGase induced gel. Light microscopy and low-field nuclear magnetic resonance results indicated with EGCG content increasing, pores and structure of double-crosslinked gels became smaller and denser, T 22 decreased from 266.162 ms to 252.845 ms and its proportion increased from 94.103% to 96.956%. Molecular docking illustrated covalent and non-covalent interactions between EGCG and myosin heavy chain Ⅱ A, and confirmed TGase catalytic mechanism with myosin heavy chain Ⅱ A as substrate. Therefore the mixture of EGCG and TGase could be used as novel cross-linker in surimi. [ABSTRACT FROM AUTHOR]