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Optimization of the thrombin inhibitory activities of different enzymatic hydrolysates was conducted, and then an optimal hydrolysis condition by trypsin (5000 u/g) was determined as follows, digested at 45 °C and pH 8.5 for 2 h with a protein concentration of 25 mg/mL. Thrombin inhibitory activity was proved to be 76.92 ± 4.66% under this condition. A total of 39 peptides were identified in the hydrolysate by UPLC-Q-TOF–MS/MS, and all the peptides were predicted to be nontoxic by in silico predictive approaches. Twenty-six peptides were predicted to be anticoagulant peptides by molecular docking method, and the peptide 26 (Lys-Asn-Ala-Glu-Asn-Glu-Leu-Gly-Glu-Val-Thr-Val-Arg) was predicted to be a better anticoagulant peptide through both structure–activity relationship and affinity activity to thrombin. The interactional positions between peptide and thrombin were also involved in the interaction site on the S1 pocket of thrombin and strongly promoted its thrombin inhibitory activity. The firmly non-bonded interactions made the bound of peptide and thrombin firmly. Eventually, the chemical identification and activity verification of synthetic peptide 26 were conducted, and the thrombin inhibitory activity was 89.96 ± 5.30% at the concentration of 9 mg/mL. This study optimized an enzymatic hydrolysis and a virtual screening method for predicting and verifying the anticoagulant peptide from Mytilus edulis, respectively, which provided a good theoretical basis and application method for the research and development of the anticoagulant peptides, especially from the seafood products.

Ruditapes philippinarum is nutrient-rich and widely-distributed, but little attention has been paid to the identification and characterization of the bioactive peptides in the bivalve. In the present study, we evaluated the peptides of the R. philippinarum that were enzymolysised by trypsin using a combination of ultra-performance liquid chromatography separation and electrospray ionization quadrupole time-of-flight tandem mass spectrometry, followed by data processing and sequence-similarity database searching. The potential allergenicity of the peptides was assessed in silico.; Results: The enzymolysis was performed under the conditions: E:S 3:100 (w/w), pH 9.0, 45 °C for 4 h. After separation and detection, the Swiss-Prot database and a Ruditapes philippinarum sequence database were used: 966 unique peptides were identified by non-error tolerant database searching; 173 peptides matching 55 precursor proteins comprised highly conserved cytoskeleton proteins. The remaining 793 peptides were identified from the R. philippinarum sequence database. The results showed that 510 peptides were labeled as allergens and 31 peptides were potential allergens; 425 peptides were predicted to be nonallergenic.; Conclusion: The abundant peptide information contributes to further investigations of the structure and potential function of R. philippinarum. Additional in vitro studies are required to demonstrate and ensure the correct production of the hydrolysates for use in the food industry with respect to R. philippinarum. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

Casein has been recognized as a good source of bioactive peptides that can be used for the production of functional food. In this study, thrombin inhibitory peptides from casein were screened by bioinformatics based on sequences predicted from in silico enzymatic digestion with trypsin, and identified by UPLC-Q-TOF-MS/MS with Mascot analysis. Molecular docking was conducted using the software of Discovery Studio 2017 to provide the potential mechanism underlying the thrombin inhibitory activity of the peptides. A total of 35 novel peptides with thrombin inhibitory activity were identified. Moreover, FQSEEQQQTEDELQDK, derived from beta-casein (fragment 33–48), showed a remarkable sequence similarity with fragment 54–65 of hirudin, and exhibited strong inhibitory activity against thrombin. FQSEEQQQTEDELQDK had similar target domain (Lys36-Gln38-Arg73-Thr74-Lys81-Ile82-Lys110) on the stereo structure of thrombin compared with hirudin. This domain belongs to the partial structure of the active site 2 of thrombin (PDB: 2BVR ), and it also located at the exosite I motif buried in the external surface of thrombin molecule, with potential inhibitory activity of the peptide.

Mytilus edulis is a typical marine bivalve mollusk. Many kinds of bioactive components with nutritional and pharmaceutical activities in Mytilus edulis were reported. In this study, eight different parts of Mytilus edulis tissues, i.e., the foot, byssus, pedal retractor muscle, mantle, gill, adductor muscle, viscera, and other parts, were separated and the proteins from these tissues were prepared. A total of 277 unique peptides from the hydrolysates of different proteins were identified by UPLC-Q-TOF-MS/MS, and the molecular weight distribution of the peptides in different tissues was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The bioactivity of the peptides was predicted through the Peptide Ranker database and molecular docking. Moreover, the peptides from the adductor muscle were chosen to do the active validation of anticoagulant activity. The active mechanism of three peptides from the adductor muscle, VQQELEDAEERADSAEGSLQK, RMEADIAAMQSDLDDALNGQR, and AAFLLGVNSNDLLK, were analyzed by Discovery Studio 2017, which also explained the anticoagulant activity of the hydrolysates of proteins from adductor muscle. This study optimized a screening and identification method of bioactive peptides from enzymatic hydrolysates of different tissues in Mytilus edulis.

Ruditapes philippinarum is nutrient-rich and widely-distributed, but little attention has been paid to the identification and characterization of the bioactive peptides in the bivalve. In the present study, we evaluated the peptides of the R. philippinarum that were enzymolysised by trypsin using a combination of ultra-performance liquid chromatography separation and electrospray ionization quadrupole time-of-flight tandem mass spectrometry, followed by data processing and sequence-similarity database searching. The potential allergenicity of the peptides was assessed in silico.The enzymolysis was performed under the conditions: E:S 3:100 (w/w), pH 9.0, 45 °C for 4 h. After separation and detection, the Swiss-Prot database and a Ruditapes philippinarum sequence database were used: 966 unique peptides were identified by non-error tolerant database searching; 173 peptides matching 55 precursor proteins comprised highly conserved cytoskeleton proteins. The remaining 793 peptides were identified from the R. philippinarum sequence database. The results showed that 510 peptides were labeled as allergens and 31 peptides were potential allergens; 425 peptides were predicted to be nonallergenic.The abundant peptide information contributes to further investigations of the structure and potential function of R. philippinarum. Additional in vitro studies are required to demonstrate and ensure the correct production of the hydrolysates for use in the food industry with respect to R. philippinarum. © 2017 Society of Chemical Industry.

The blue mussel (Mytilus edulis) reportedly contains many bioactive components of nutritional value. Water-, salt- and acid-soluble M. edulis protein fractions were obtained and the proteins were trypsinized. The resultant peptides were analyzed by ultra-performance liquid chromatography quadrupole time of flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). 387 unique peptides were identified that matched 81 precursor proteins. Molecular mass distributions of the proteins and peptides were analyzed by sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE). The differences between the three protein samples were studied by Venn diagram of peptide and protein compositions. Toxicity, allergic and antithrombotic activity of peptides was predicted using database website and molecular docking respectively. The antithrombotic activity of enzymatic hydrolysate from water-, salt- and acid-soluble M. edulis protein were 40.17%, 85.74%, 82.00% at 5 mg/mL, respectively. Active mechanism of antithrombotic peptide (ELEDSLDSER) was also research about amino acid binding sites and interaction, simultaneously.