豆浆成分对Bowman-Birk胰蛋白酶抑制剂热失活程度的影响

Effect of Soymilk Components on Inactivation Degree of Bowman-Birk Inhibitor

建立葡萄糖+Bowman-Birk胰蛋白酶抑制剂(Bowman-Birk inhibitor,BBI)、果糖+BBI和大豆蛋白+BBI模型体系考察还原糖、大豆蛋白及热处理3个因素对BBI热失活的贡献程度。结果显示:未加热条件下,葡萄糖有增强BBI活性的作用,果糖无此作用。加热条件下,还原糖对BBI的胰蛋白酶抑制活性(trypsin inhibitor activity,TIA)影响很大,而对胰凝乳蛋白酶抑制活性(chymotrypsin inhibitor activity,CIA)影响非常小;葡萄糖对BBI的TIA影响程度比果糖大;大豆蛋白对BBI的CIA影响程度大于TIA;BBI可与大豆球蛋白的碱性肽链形成二聚体,也可与大豆球蛋白形成多聚体;BBI可形成二聚体。在还原糖、大豆蛋白和BBI质量浓度均为2 mg/mL的情况下(沸水浴3 h),对于TIA失活:葡萄糖>热诱导构象改变>果糖>大豆蛋白;对于CIA失活:大豆蛋白>热诱导构象改变>葡萄糖/果糖。

Considering that soymilk is a complex system,this study designed three model systems(glucose+Bowman-Birk inhibitor(BBI),fructose+BBI,and soybean protein(SP)+BBI)to examine the contribution of reducing sugar,SP and heat treatment to BBI inactivation.Without heating,glucose could enhance the activity of BBI,but fructose could not.With heating,reducing sugar could obviously affect trypsin inhibitor activity(TIA)of BBI,but only slightly affect its chymotrypsin inhibitor activity(CIA);glucose affected BBI more obviously than did fructose.SP could affect CIA of BBI more obviously than its TIA;BBI could link to basic peptide chains of glycinin by disulfide bonding to form a dimer,and also could interact with SP to form a polymer by disulfide bonding;in addition,BBI could interact with itself to form a BBI dimer.Under the conditions of incubation in boiling water bath for 3 h,and BBI,glucose,fructose,and SP concentrations of 2 mg/mL,glucose made the greatest contribution to TIA inactivation,followed by heat-induced conformation change,fructose and SP,while SP made the greatest contribution to CIA inactivation,followed by heat-induced conformation change,and glucose/fructose.