Isolation and identification of thrombin-inhibiting peptides derived from soybean protein

The aim of this study was preparation of a soybean protein hydrolyzate with thrombin inhibitory activity and isolation, identification, and characterization of the active peptides from the hydrolyzate. In this study, a soybean protein hydrolyzate with the thrombin inhibiting IC50 value of 2.78 mg/mL was prepared under the improved pepsin hydrolysis condition, which exhibited the highest thrombin inhibitory activity in these soybean protein-derived hydrolyzates. A novel nonapeptide FFPDIPKIK with the IC50 value of 2.36 mM was screened from the hydrolyzate by in silico methods. The kinetic studies and molecular docking showed that the nonapeptide adopted a mixed-type mode to inhibit thrombin and bound with thrombin with several hydrogen bonds and hydrophobic interactions. The nonapeptide was partially digested using the in vitro digestion model, and its truncated peptides had comparable thrombin inhibitory activity. The results suggested that soybean protein hydrolyzate could be exploited as a functional food ingredient against coagulation.