Search

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.