关键词: 牡蛎, 酶解, ACE抑制肽, 分子质量分布, 氨基酸组成

Abstract: The stepwise enzymatic hydrolysis of Pacific oyster (Crassostrea gigas) for preparing angiotensin-Ⅰ converting enzyme (ACE) inhibitory peptides was optimized by orthogonal array design and response surface methodology (RSM). Pacific oyster was sequentially hydrolyzed by protamex followed by alcalase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and ACE inhibitory activity analysis were used to determine the optimal hydrolysis conditions. The results showed that the optimal conditions for the first hydrolysis step were determined as follows: solid to liquid ratio, 1:4 (g/mL); pH, 7.0; protamex dosage, 1.2%; hydrolysis duration, 1 h, and those for the second hydrolysis step were temperature were 53 ℃; pH, 8.3; alcalase dosage, 0.42%, and hydrolysis duration, 73 min. Gel filtration chromatography analysis showed that the molecular masses of almost all (99.72%) the peptides produced were lower than 3 000 D. Meanwhile, the oyster peptides revealed high ACE inhibitory activity, with IC50 of 0.8 mg/mL. Amino acid composition analysis indicated that glutamic acid was the most abundant amino acid while cysteine was the least abundant one in the peptide products. Among the total amino acids, essential amino acids accounted for 36.6% while hydrophobic amino acids accounted for 37.2%. Our present work can provide a theoretical reference for the development of antihypertensive peptides derived from oyster.

Key words: oyster, hydrolysis, ACE inhibitory peptide, molecular mass distribution, amino acid composition