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Thrombotic disease refers to the disease caused by thrombosis and thromboembolism. In recent years, the global incidence and mortality rates of thromboembolic diseases has increased significantly, posing a serious threat to human life and health. Since ancient times, anticoagulant has been an important way to prevent and treat thrombotic diseases. However, anticoagulant tolerance and side effects have appeared in its clinical applications. Food-derived bioactive peptides have the advantages of high bioavailability and safety and are very promising in the prevention and treatment of thrombotic diseases. This paper summarizes the sources, preparation, purification, identification, anticoagulant activity and mechanisms of food-derived antithrombotic peptides in order to provide a reference for the future development of food-derived antithrombotic peptides and new anticoagulants.

To explore the changes in the viability and taste compounds of Crassostrea gigas at different circulation stages after harvesting, the oysters were sampled at different times of depuration, induced dormancy and waterless live storage for evaluation of viability changes in terms of adenosine triphosphate (ATP) related compounds, adenylate energy charge (AEC) and free amino acids and evaluation of flavor quality changes with respect to contents and taste activity values (TAV) of taste compounds. The results showed that the viability and taste compounds of C. gigas were significantly influenced by postharvest transportation and environmental stress. All viability indicators were significantly restored by 24 h depuration, with ATP, AEC and the content of total free amino acids being significantly higher than before depuration (P < 0.05), indicating that the viability reached new levels. During the process from induced dormancy to waterless live storage, more energy substances were required to maintain the balance of the organism under low temperature and hypoxia stress, so all viability indicators were significantly lower than before depuration (P < 0.05) and remained stable at a lower level. Among the taste compounds, the content of umami amino acids increased and the content of bitter amino acids decreased in C. gigas after depuration, and the content of taste amino acids decreased slowly as the waterless live storage time increased. The umami?nucleotides inosine 5’-monphosphate (IMP) and adenosine 5’-monophosphate (AMP) were accumulated throughout the circulation process (P < 0.05); the total amount of organic acids showed a fluctuant downward trend, with the amount of lactic acid being significantly higher after than before depuration (P < 0.05) and showing a decreasing trend from dormancy to the end of waterless live storage (P < 0.05), while the amounts of succinic acid and malic acid showed an increasing trend during waterless live storage (P < 0.05). The levels of Na+ and K+, which play an auxiliary role in the umami taste of C. gigas, were higher after 9 days of waterless live storage than before depuration. The total amount of taste substances did not change overall. The TAV of taste compounds showed that Asp, Glu, Arg, Ala, IMP, lactic acid, succinic acid, Na+ and K+ contributed significantly to the taste of C. gigas. In conclusion, the viability and taste substances of C. gigas can be maintained at a high level by depuration for 24 hours + gradient cooling to induce dormancy + ecological ice temperature waterless live storage for 9 days after harvesting.

For thousands of years, pearl and nacre powders have been important traditional Chinese medicines known for their skin whitening effects. To prepare the enzymatic hydrolysates of Hyriopsis cumingii nacre powder (NP-HCH), complex enzymatic hydrolysis by pineapple protease and of neutral protease was carried out after the powder was pre-treated with a high-temperature and high-pressure method. The peptides were identified using LC-MS/MS and picked out through molecular docking and molecular dynamics simulations. Subsequently, the tyrosinase inhibitory and antioxidant properties of novel tyrosinase inhibitory peptides were investigated in vitro. In addition, the enzymatic activity of tyrosinase in B16F10 cells as well as melanin content and antioxidant enzyme levels were also examined. The results showed that a tyosinase inhibitory peptide (Tyr-Pro-Asn-Pro-Tyr, YPNPY) with an efficient IC50 value of 0.545 ± 0.028 mM was identified. The in vitro interaction results showed that YPNPY is a reversible competitive inhibitor of tyrosinase, suggesting that it binds to the free enzyme. The B16F10 cell whitening test revealed that YPNPY can reduce the melanin content of B16F10 cells by directly inhibiting the activity of intracellular tyrosinase. Additionally, it indirectly affects melanin production by acting as an antioxidant. These results suggest that YPNPY could be widely used as a tyrosinase inhibitor in whitening foods and drugs. [ABSTRACT FROM AUTHOR]

Colitis causes inflammation, diarrhoea, fever, and other serious illnesses, posing a serious threat to human health and safety. Current medications for the treatment of colitis have serious side effects. Therefore, the new strategy of creating a defence barrier for immune function by adding anti-inflammatory foods to the daily diet is worth advocating for. Low-molecular weight oyster peptides (LOPs) are a natural food with anti-inflammatory activity extracted from oysters, so intervention with LOPs is likely to be an effective preventive solution. The aim of this study was to investigate the preventive effect of LOPs on lipopolysaccharide (LPS)-induced acute colitis inflammation in mice and its underlying mechanism. The results showed that LOPs not only inhibited the colonic histopathy in mice induced by LPS-induced inflammation but also reduced the inflammatory response in the blood. In addition, LOPs significantly increased the number of beneficial bacteria (Alistipes, Mucispirillum, and Oscillospira), decreased the number of harmful bacteria (Coprobacillus, Acinetobater) in the intestinal microbiota, and further affected the absorption and utilisation of short-chain fatty acids (SCFAs) in the intestinal tract. In conclusion, dietary supplementation with LOPs is a promising health-promoting dietary supplement and nutraceutical for the prevention of acute colitis by reducing the inflammatory response and modulating the intestinal microbial communities. [ABSTRACT FROM AUTHOR]

The inhibition of dipeptidyl peptidase-IV (DPP-IV) is a promising approach for regulating the blood glucose levels in patients with type 2 diabetes (T2D). Oysters, rich in functional peptides, contain peptides capable of inhibiting DPP-IV activity. This study aims to identify the hypoglycemic peptides from oysters and investigate their potential anti-T2D targets and mechanisms. This research utilized virtual screening for the peptide selection, followed by in vitro DPP-IV activity assays to validate the chosen peptide. Network pharmacology was employed to identify the potential targets, GO terms, and KEGG pathways. Molecular docking and molecular dynamics simulations were used to provide virtual confirmation. The virtual screening identified LRGFGNPPT as the most promising peptide among the screened oyster peptides. The in vitro studies confirmed its inhibitory effect on DPP-IV activity. Network pharmacology revealed that LRGFGNPPT exerts an anti-T2D effect through multiple targets and signaling pathways. The key hub targets are AKT1, ACE, and REN. Additionally, the molecular docking results showed that LRGFGNPPT exhibited a strong binding affinity with targets like AKT1, ACE, and REN, which was further confirmed by the molecular dynamics simulations showcasing a stable peptide–target interaction. This study highlights the potential of LRGFGNPPT as a natural anti-T2D peptide, providing valuable insights for potential future pharmaceutical or dietary interventions in T2D management. [ABSTRACT FROM AUTHOR]

Pearl and nacre powders have been valuable traditional Chinese medicines with whitening properties for thousands of years. We utilized a high-temperature and high-pressure method along with compound enzyme digestion to prepare the enzymatic hydrolysates of nacre powder of Pinctada martensii (NP-PMH). The peptides were identified using LC–MS/MS and screened through molecular docking and molecular dynamics simulations. The interactions between peptides and tyrosinase were elucidated through enzyme kinetics, circular dichroism spectropolarimetry, and isothermal titration calorimetry. Additionally, their inhibitory effects on B16F10 cells were explored. The results showed that a tyrosinase-inhibitory peptide (Ala-His-Tyr-Tyr-Asp, AHYYD) was identified, which inhibited tyrosinase with an IC50 value of 2.012 ± 0.088 mM. The results of the in vitro interactions showed that AHYYD exhibited a mixed-type inhibition of tyrosinase and also led to a more compact enzyme structure. The binding reactions of AHYYD with tyrosinase were spontaneous, leading to the formation of a new set of binding sites on the tyrosinase. The B16F10 cell-whitening assay revealed that AHYYD could reduce the melanin content of the cells by directly inhibiting the activity of intracellular tyrosinase. Additionally, it indirectly affects melanin production by acting as an antioxidant. These results suggest that AHYYD could be widely used as a tyrosinase inhibitor in whitening foods and pharmaceuticals. [ABSTRACT FROM AUTHOR]

Summary: Enzymatic supramolecular assembly was applied to increase the thermal hysteresis activity (THA) of tilapia skin collagen peptides and their applicability as cryoprotectants. The THA value of the glutamine‐assembled product increased by 61.5% and its ice crystal content dropped by 33.93% compared to the collagen peptides. Following initial separation and purification, the THA of Gln‐AFPs was further elevated by 28.6%. After five freeze–thaw cycles, tilapia surimi treated with 8% Gln‐AFPs had high levels of salt‐soluble protein, total sulfhydryl content, Ca2+‐ATPase activity, and water‐holding capacity. Additionally, the cryoprotective effect of Gln‐AFPs on the surimi was found to be superior to that of commercial antifreeze. The majority of the Gln‐AFPs turns folded, according to FTIR analysis, and ‐helices were produced. After supramolecular assembly, the Gln‐AFPs structure also smoothed out. As a result, the enzymatic supramolecular assembly drastically increased the antifreeze activity of the tilapia skin‐collagen peptides, which could eventually be developed into a novel antifreeze additive in the food industry. [ABSTRACT FROM AUTHOR]

Summary: The present study aimed to comparatively analyse the functional properties of the spray drying particles prepared from the noble scallop (Chlamys nobilis) mantle protein‐pectin hydrated mixtures. And the microstructural characteristics of the particles were assessed by Fourier transform infrared, scanning electronic microscopy, and SDS‐PAGE to detect critical changes. The results showed that the solubility of enzymatically extracted protein was significantly improved by spray drying after pectin hydration (AP‐LMP and AP‐HMP), from 76.77% (AP) to 97.87% (AP‐LMP) and 97.13% (AP‐HMP), respectively. And the spray drying water‐extracted protein (HP) after pectin hydration (HP‐LMP and HP ‐HMP) exhibited a greater emulsifying property, from 103.10 m2/g (HP) to 145.55 ± 0.92 m2/g (HP‐LMP) and 200.29 ± 1.16 m2/g (HP‐HMP). The spray drying after pectin hydration had successfully enhanced emulsifying and rheological properties when compared with AP and HP. The results of SDS‐PAGE showed more protein participated in the formation of macromolecule and FT‐IR spectra demonstrated the formation of protein‐pectin spray drying particles facilitated not only by electrostatic interactions but also by covalent binding via Maillard reaction, made a closely compatible protein structure verified by the improvement of fluorescence intensity. This work is expected to provide a theoretical basic data for the development and application of scallop mantle extracted proteins. [ABSTRACT FROM AUTHOR]

Oysters contain significant amounts of the zinc element, which may also be found in their proteins. In this study, a novel zinc-binding protein was purified from the mantle of the oyster Magallana hongkongensis using two kinds of gel filtration chromatograms. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) showed that its molecular weight was approximately 36 kDa. The protein identified by the Q-Exactive mass spectrometer shared the highest sequence identity with carbonic anhydrase derived from Crassostrea gigas concerning amino acid sequence similarity. Based on homologous cloning and RACE PCR, the full-length cDNA of carbonic anhydrase from Magallana hongkongensis (designated as MhCA) was cloned and sequenced. The cDNA of MhCA encodes a 315-amino-acid protein with 89.74% homology to carbonic anhydrase derived from Crassostrea gigas. Molecular docking revealed that the two zinc ions primarily form coordination bonds with histidine residues in the MhCA protein. These results strongly suggest that MhCA is a novel zinc-binding protein in Magallana hongkongensis. [ABSTRACT FROM AUTHOR]

This study aimed to purify and characterize immunoregulatory peptides from Sipunculus nudus L. and to explore the underlying mechanisms. Ultrafiltration, gel filtration chromatography, and reverse phase high‐performance liquid chromatography (RP‐HPLC) were used to purify the peptide following enzymatic hydrolysis. Rates of lymphocyte proliferation and phagocytosis as well as nitric oxide (NO) production levels were used as indicators of immunoregulatory activity to screen the fractions. The amino acid sequence of the peptide, designated as SNLP, was identified as Arg–Val–Lys–Gly–Lys–Ile–Leu–Ala–Lys–Arg–Leu–Asn (RVKGKILAKRLN) by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Treatment with the synthetic SNLP increased the proliferation and phagocytosis of RAW 264.7 macrophages and promoted the secretion of tumor necrosis factor‐ɑ (TNF‐α), interleukin‐6 (IL‐6), interleukin‐1β (IL‐1β), and NO levels. The mRNA levels of these cytokines and iNOS were also increased by SNLP. Our results provide preliminary evidence suggesting that SNLP acts as a dual immunomodulatory peptide with immunostimulatory and anti‐inflammatory activities. In summary, SNLP derived from Sipunculus nudus L. is a potent immunoregulatory peptide and represents a potential functional food or immunoregulatory drug. [ABSTRACT FROM AUTHOR]

Summary: Litopenaeus vannamei heads were autolysed at a constant temperature of 50 °C, pH 7.0 for a maximum duration of 5 h, and the antifreeze activity and physicochemical properties of the head autolysates were determined. Thermal hysteresis (TH) was used as an index for determining the antifreeze activity of the shrimp head autolysates. The highest thermal hysteresis activity was 1.82 °C which was measured in the 5 h‐shrimp head autolysate. The highest negative zeta potential value (−41.06 ± 2.08 mV) and surface hydrophobicity (295.575 ± 9.7819) were in the 5 and 1.5 h autolysate groups, respectively. Generally, <2000 Da components accounted for over 85% of the total molecular weight in all shrimp head autolysate groups. Pearson correlation analysis was used to investigate how physicochemical properties influenced the thermal hysteresis index. Although at varying degrees, the analysis confirmed that a positive correlation existed between TH activity and molecular weight, hydrophobic amino acid content, and surface hydrophobicity. A negative correlation existed between TH activity and zeta potential, and hydrophilic amino acids. The findings of our study suggest that Litopenaeus vannamei head autolysate has a potential antifreeze effect and that the physicochemical properties influence its thermal hysteresis. [ABSTRACT FROM AUTHOR]

In order to realize the multi-level utilization of marine shellfish resources and to develop the potential biological activity of processing by-products of Atrina pectinata, gelatin was extracted from the mantle and the potential whitening effect of its enzymatic peptides was explored. Taking tyrosinase inhibitory activity as the evaluation index, the enzyme hydrolysate process was optimized by response-surface methodology, and the optimal enzyme hydrolysate conditions were as follows: pH 5.82, 238 min enzyme hydrolysate time, and temperature of 54.5 °C. Under these conditions, the tyrosinase inhibition activity of Atrina pectinata mantle gelatin peptide (APGP) was 88.6% (IC50 of 3.268 ± 0.048 mg/mL). The peptides obtained from the identification were separated by ultrafiltration and LC–MS/MS, and then four new peptides were screened by molecular docking, among which the peptide Tyr-Tyr-Pro (YYP) had the strongest inhibitory effect on tyrosinase with an IC50 value of 1.764 ± 0.025 mM. The molecular-docking results indicated that hydrogen bonding is the main driving force for the interaction of the peptide YYP with tyrosinase. From the Lineweaver–Burk analysis, it could be concluded that YYP is inhibitory to tyrosinase and exhibits a mixed mechanism of inhibition. These results suggest that YYP could be widely used as a tyrosinase inhibitor in whitening foods and pharmaceuticals. [ABSTRACT FROM AUTHOR]

In order to tap the potential of high-value utilization of Chlamys nobilis, using compound protease to hydrolyze Chlamys nobilis adductor muscle, the effect of EHCA(enzymatic hydrolysate of Chlamys nobilis adductor muscle) on the activity of α-glucosidase and the scavenging ability of DPPH free radicals was explored. The fasting blood glucose concentration, serum insulin content, liver malondialdehyde and superoxide dismutase content were used as indicators to evaluate the auxiliary hypoglycemic function and antioxidant activity of EHCA in normal mice. The results showed that EHCA had good a-glucosidase inhibitory activity, and its DPPH free radical scavenging ability increased with the concentration of the enzymatic hydrolysate. The results of animal experiments showed that a certain concentration of EHCA could enhance the glucose tolerance of mice, significantly reduced the liver malondialdehyde and increase the activity of superoxide dismutase. In conclusion, the compound protease can effectively enzymolyze the adductor muscle of Chlamys nobilis, and its enzymatic hydrolysate has good α-glucosidase inhibitory activity and antioxidant activity with a certain auxiliary hypoglycemic effect. The results may provide a theoretical basis for the development of auxiliary hypoglycemic marine functional foods. [ABSTRACT FROM AUTHOR]

Oysters are nutritious and tasty but difficult to store. Drying can extend the storage period of oysters and give them a unique flavor. In this study, the effects of four drying procedures, namely, vacuum freeze drying (VFD), vacuum drying (VD), natural sun-drying (NSD), and hot air drying (HAD), on the flavor characteristics of oysters (Crassostrea hongkongensis) were investigated using blanched oysters as a control (CK). Results showed that HAD produced more free amino acids than the other methods, but VFD retained the most flavor nucleotides. Compared with cold drying (VFD), hot drying (VD, NSD, and HAD) increased the abundance of organic acids, betaine, and aroma substances. Glutamic acid, alanine, AMP, hexanal, octanal, heptanal, (E, E)-2,4-heptadienal, (E)-2-decenal, nonanal, etc., are defined as the characteristic flavor compounds of dried oysters, with umami, sweet, green, fatty, and fruity aromas being the main organoleptic attributes of dried oysters. Glutamic acid, glycine, betaine, IMP, pentanal, ethyl heptanoate, (E, Z)-2,4-nonadienal, 1-octen-3-one, 2-hexenal, 2-octenal, hexanal, decanal were defined as markers to distinguish different drying methods. Overall, HAD showed improved flavor qualities and characteristics and was better suited for the highly commercialized production of dried oysters. [ABSTRACT FROM AUTHOR]

This study focuses on the critical connection area between type IV hydrogen storage vessels and external valves, which is commonly referred to as the BOSS structure. The novel BOSS structures were proposed to further ensure the safety of pressure vessels. In order to identify optimal structure that meet industrial requirements, finite element models were performed to analyze and compare the effectiveness of the proposed models in terms of strength, fatigue, and sealing performance. Some influences were discussed, including the angle of inclination of the stop-rotation platform and the number of sealing grooves in the BOSS structures. The results showed that the fatigue life of the proposed BOSS structures can exceed the design life of 30,000 cycles using austenitic stainless steel S31603. The maximum contact stresses were higher than the operating pressure of 58 MPa. Additionally, The BOSS structure model designed with a stop-rotation platform featuring a 65° tilt angle and two sealing grooves had the lowest mean square deviation of contact stress, which was 13.47 MPa, indicating reliable sealing performance. [ABSTRACT FROM AUTHOR]

Summary: Previous studies have found that UV‐C irradiation activated endogenous acid protease (EAP) in shrimp heads. Aiming at understanding the effect of UV‐C irradiation on the activation of EAP and improving the utilisation of EAP, the effect of UV‐C irradiation on the enzymatic properties and conformation of EAP was investigated. The enzymatic properties of EAP were unaltered after UV‐C irradiation, and the optimum pH, temperature, and NaCl concentration were 3, 60°C, and 0.5 mol/L, respectively. Ca2+ and Mg2+ activated the enzyme. The molecular weight of the purified endogenous acid protease (P‐EAP) was 32 kDa. UV–Vis, FTIR, circular dichroism, and fluorescence spectroscopy indicated that the increase in enzyme activity by UV‐C irradiation was related to an increase in tryptophan and hydrogen bonding, implying that it may be the change in the spatial structure of the protein that caused the activation of the enzyme. Results revealed that UV‐C irradiation can be used to activate proteases and provide a reference for enhancing the enzymatic activity of other enzymes from shrimp heads. [ABSTRACT FROM AUTHOR]

Summary: A novel natural zinc‐enriched polysaccharide: OZPs‐1 was isolated from oyster (Crassostrea hongkongensis), with 922.18 μg g−1 of zinc. The physicochemical properties and structural features of OZPs‐1 were systematically studied. The results showed OZPs‐1 was predominantly composed of glucose, with a molecular weight ranging from 4 to 2044 kDa. OZPs‐1 showed favourable thermal stability. NMR analysis showed that there was no sulphate substitution and C‐6 substitution in OZPs‐1, while C‐4 might be the binding site of zinc and polysaccharide. UV, FTIR and XRD spectra suggested ‐OH and ‐COOH group might be involved in the binding of zinc to polysaccharides in OZPs‐1 and there were no ZnO and sulphate substitutions in OZPs‐1. These conclusions indicated that zinc might bind with ‐OH and ‐COOH in C‐4 of polysaccharides and impart the stable structure and favourable physicochemical properties of OZPs‐1, which could facilitate the application of OZPs‐1 as natural organic zinc supplements. [ABSTRACT FROM AUTHOR]

This study aimed to purify and identify antiphotoaging peptides from oyster (Crassostrea hongkongensis) protein enzymatic hydrolysates (OPEH) and to investigate the possible mechanism underlying its antiphotoaging effect. Multiple methods (Ultrafiltration, G25 Chromatography, RP-HPLC, and LC/MS/MS) had been used for this purpose, and eventually, two peptides, including WNLNP and RKNEVLGK, were identified. Particularly, WNLNP exerted remarkable antiphotoaging effect on the UVB-irradiated HaCaT photoaged cell model in a dose-dependent manner. WNLNP exerted its protective effect mainly through inhibiting ROS production, decreasing MMP-1 expression, but increasing extracellular pro-collagen I content. Furthermore, WNLNP downregulated p38, JNK, ERK, and p65 phosphorylation in the MAPK/NF-κB signaling pathway and attenuated bax over-expressions but reversed bcl-2 reduction in UVB- irradiated HaCaT cells. The molecular docking analysis showed that WNLNP forms five and seven hydrogen bonds with NF-κB (p65) and MMP-1, respectively. This study suggested that a pentapeptide WNLNP isolated from OPEH had great potential to prevent and regulate skin photoaging. [ABSTRACT FROM AUTHOR]

Currently, the processing method of introducing plant protein into meat products has attracted great attention. However, the direct addition of plant protein often leads to a decline in meat product quality. This paper aims to provide an efficient method for incorporating plant protein into fish sausage. Pea protein isolate (PPI), grass carp protein isolate (CPI) and pea-grass carp coprecipitated dual protein (Co) were derived from pea and grass carp by an isoelectric solubilisation/precipitation method. At the same time, the blended dual protein (BL) was obtained by blending PPI with CPI, and the plant and animal protein content of Co and BL was both controlled to be the same. The four proteins were combined with soybean oil and water to form a three-phase pre-emulsification system of protein-oil-water, which was added to grass carp meat as a replacement for animal fat to prepare fish sausage. The gelation properties of the four fish sausages and those without protein were analysed. The results showed that the gel quality of PPI fish sausage is poor, while the overall quality of Co fish sausage as a whole was significantly superior to that of PPI and BL, which was equivalent to CPI fish sausage. The sensory score of the Co fish sausage was slightly lower than that of CPI, but it had significantly higher water-holding capacity and hardness (p < 0.05). The Co fish sausage showed the synergistic effect of heterologous proteins, while BL had some antagonistic effects. This study shows that Co pre-emulsion is an effective strategy to introduce plant protein, so it has a good application prospect in the meat industry. [ABSTRACT FROM AUTHOR]

Isoelectric solubilisation/co-precipitation (ISP) has been proven to be a better method than blending for preparing plant–animal dual-proteins, which can achieve synergies in the functional properties of heterologous proteins. This paper aims to investigate the effect of extraction pH on the functional properties of co-precipitated dual-protein. The basic composition, subunit composition, solubility, surface hydrophobicity, emulsification and gel properties of co-precipitated dual-protein (Co) prepared from pea and grass carp with pH (2.0, 3.0, 9.0, 10.0 and 11.0) were analysed in this study using ISP. The results showed that the functional properties of Co (Co9, Co10, Co11) prepared by alkali extraction were generally better than those prepared by acid extraction (Co2, Co3). Among them, Co10 has the highest vicilin/legumin α + β value and solubility, while having the lowest surface hydrophobicity, making its emulsification and gel properties superior to other extraction pH values. This study provides an important method reference for preparing plant-animal Co with exceptional functional properties. [ABSTRACT FROM AUTHOR]

Protein content, a vital component determining the nutritional quality of oysters, is unevenly distributed in different parts of oyster. In this study, the spatial distribution (visceral mass, mantle, gill, and adductor) patterns and structural characteristics of proteins, including water–soluble proteins (WSP), salt–soluble proteins (SSP), acid–soluble proteins (ASP) and alkali–soluble proteins (ALSP) of oysters (Crassostrea hongkongensis) were investigated with the amino acid analyzer, circular dichroism spectroscopy (CD), fourier transform infrared spectroscopy (FTIR), and fluorescence spectroscopy. The results showed that oyster proteins were mainly distributed in the visceral mass and mantle. The protein composition was WSP, SSP, ALSP, and ASP in descending order, which conformed to the ideal amino acid pattern. Variations in secondary structure, molecular weight distribution, and thermal denaturation temperatures of the oyster proteins were observed. SSP had wider bands (16–270 kDa) than those of ASP (30–37 kDa) and ALSP (66–270 kDa). Among the four proteins, the SSP of the mantle showed the highest thermal stability (87.4 °C), while ALSP of the adductor muscle had the lowest the lowest the peak denaturation temperature (Tm) (53.8 °C). The proportions of secondary structures in oyster proteins were different, with a higher proportion of solid protein β–folds, and the exposure of aromatic amino acid residues and disulfide bonds and the microenvironment in which they were located were also different. [ABSTRACT FROM AUTHOR]