中文摘要：

运用正交试验和响应面法优化牡蛎血管紧张素转换酶（angiotensin-Ⅰconvertingenzyme，ACE）抑制肽的分步酶解制备工艺。采用复合蛋白酶和碱性蛋白酶对牡蛎进行分步酶解，以十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodiumdodecylsulfate-polyacrylamidegelelectrophoresis，SDS-PAGE）分析和ACE抑制率为考核指标优化工艺参数。结果表明，第1步复合蛋白酶最佳工艺参数为：料液比1∶4、加酶量1.2%、pH7.0、反应温度50℃、酶解时间1h；第2步碱性蛋白酶最佳工艺参数为：加酶量0.42%、pH8.3、反应温度53℃、酶解时间73min。凝胶过滤色谱法测得牡蛎酶解液分子质量在3000D以下小肽所占比例为99.72%，其ACE抑制活性IC50为0.8mg/mL。同时，氨基酸组成分析表明，牡蛎肽中Glu含量最高，Cys含量最低；必需氨基酸和疏水性氨基酸含量分别占总氨基酸的36.6%和37.2%。本研究制备的低分子质量、高ACE抑制活性牡蛎肽，可为牡蛎资源的开发利用提供理论参考。

英文摘要：

The stepwise enzymatic hydrolysis of Pacific oyster(Crassostrea gigas)for preparing angiotensin-Ⅰconverting 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,1h,and those for the second hydrolysis step were temperature were53℃;pH,8.3;alcalase dosage,0.42%,and hydrolysis duration,73min.Gel filtration chromatography analysis showed that the molecular masses of almost all(99.72%)the peptides produced were lower than3000D.Meanwhile,the oyster peptides revealed high ACE inhibitory activity,with IC50of0.8mg/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 for36.6%while hydrophobic amino acids accounted for37.2%.Our present work can provide a theoretical reference for the development of antihypertensive peptides derived from oyster.