Identification and Structure-activity Relationships of Antioxidant Peptides Derived from Earthworm Proteins
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Abstract:
The effects of exogenous protease pre-enzymolysis treatment on the degree of gastrointestinal digestion and antioxidant activity of earthworm proteins were examined following gastrointestinal digestion. Five proteases were used to prepare different hydrolysates of earthworm proteins, and changes in the degree of hydrolysis, molecular weight distribution, and in vitro antioxidant activities of these enzymatic hydrolysates were investigated based on simulated gastrointestinal digestion in vitro. Among these hydrolysates, the degree of hydrolysis of the alkaline protease hydrolysate was the highest at 40.81%. The rates of DPPH and ABTS free radical scavenging were 27.36 and 175.46 μmol TE/g, respectively, and the ORAC value was 0.70 μmol TE/mg. Following gastrointestinal digestion, the degree of hydrolysis, rate of DPPH free radical scavenging, and ORAC value of the alkaline protease hydrolysate increased by 94.06%, 72.21%, and 120%, respectively, compared with the products obtained via direct gastrointestinal digestion of earthworm proteins. A total of 10 823 peptides with molecular weight <3 ku were identified in GHEWP, and 11 peptides with the highest activity scores were screened using bioware.ucd.ie to determine their activity threshold score for synthesis and verification. Among these, the peptides ATSGFFVY, HCFVLY, HLASGWY, HRYSDF, and HYANMY had the highest comprehensive antioxidant capacities. The quantum chemical calculation results revealed that the active sites of ATSGFFVY, HCFVLY, HRYSDF and HYANMY might be located at Tyr-8, Tyr-6, Tyr-3, and Tyr-2, respectively, and the active site of HLASGWY may be located at Trp-6. The findings of this study indicate that pre-enzymatic hydrolysis using alkaline protease can enhance the degree of digestion of earthworm proteins and also the antioxidant activity of their gastrointestinal digestion products.
