枯草芽孢杆菌凝乳酶的酶学性质

对枯草芽孢杆菌凝乳酶的酶学性质进行了研究,结果表明:枯草芽孢杆菌凝乳酶作用的最适反应温度为55℃、最适pH值为5.0,在pH值为6.0时最稳定,在65℃保温60 min酶活基本丧失,Mn2+、Li+、Fe2+、Na+、K+、Mg2+、Ca2+对该凝乳酶有促进作用,Mg2+、Ca2+促进作用较为明显,而Cu2+对该酶有明显的抑制作用;酶修饰剂中β-巯基乙醇对凝乳酶活力的影响较小,EDTA可抑制该凝乳酶的活力;蛋白酶抑制剂σ-phenantroline可以明显抑制酶活性,证实该酶为金属蛋白酶类。在与商品酶对比中发现枯草芽孢杆菌凝乳酶与商品酶的酶学性质相近。

Enzymological Characteristics of Chymosin Produced by Bacillus subtilis

Enzymological characteristics of chymosin produced by Bacillus subtilis were studied.The results showed that the optimal temperature of chymosin was 55 ℃,and the optimal coagulating pH was 5.0.The clotting activity was more stable at pH 6.0.The enzyme almost lost activity by retaining after 60 min at 65 ℃.The metal ions Mn2+,Li+,Fe2+,Na+,K+,Mg2+ and Ca2+increased the clotting activity and Mg2+ and Ca2+ showed the greatest effect while Cu2+ inhibited the clotting activity.As enzyme modifiers,β-mercaptoethanol had no clear effect on milk-clotting activity while EDTA inhibited the clotting activity.As protein inhibitors,σ-phenantroline strongly inhibited the clotting activity,so the enzyme is a metalloproteinase. Experimental results showed that chymosin produced by Bacillus subtilis had the similar characteristics to the commercial chymosin.