Ultrasound-assisted enzymatic hydrolysis of loach (Misgurnus anguillicaudatus) protein for antioxidant peptides: process optimization, structural characterization, and Keap1/Nrf2-mediated antioxidant mechanism.

Loaches are kinds of freshwater fish rich in protein, which have high development value. Loach protein hydrolysates were prepared by ultrasound-assisted enzymatic hydrolysis. The results showed, the hydrolysate exhibited strong antioxidant activity under the following conditions: ultrasonic power of 200 W, treatment time of 22 min, and neutral enzyme dosage of 10 KU/g. The structure characterization and analysis of hydrolysates under different treatments showed that ultrasound-assisted enzymatic hydrolysis could form more bioactive peptides with hydrophobic amino acids. A total of 2289 peptide sequences were identified, and 8 ideal peptide sequences were screened by combining biological activity score, hydrophobicity and other bioinformatics indicators. The binding energy between loach peptide and Keap1-Nrf2 protein was compared via molecular docking simulation. Among them, the binding energy between FG-14 and Keap1-Nrf2 was the highest (-86.43 kJ/mol). Subsequent experiments further verified the good antioxidant effect of FG-14. This study provides theoretical and technical support for high-value utilization of loaches.