环状芽孢杆菌β-半乳糖苷酶水解乳糖和ONPG的底物特异性

在细菌乳糖酶的菌株筛选过程中发现，OHA与LHA的比值范围 1．3－32．2之间，表明OHA与LHA差异很大，无相关性。对环状芽孢杆菌的乳糖酶研究发现，Na^ 和K^ 能不同程度地促进OHA和LHA；Mg^2 能增强OHA，对LHA却表现出抑制作用。酶作用于ONPG和乳糖的最适pH和温度也存在差异。一定反应体系中，OHA／LHA的值随反应条件的变化而不同，因此用OHA来评价LHA会对酶的实际应用带来很大影响。

Specificity of the Hydrolysis Substrates of Lactose and ONPG by β-Galactosidase from Bacillus Circulans

In this paper, during the strain screening of hydrolase from Bacillus, it is found that the ratio of ONPG-hydrolyzing activity (OHA) and lactose-hydrolyzing activity (LHA) is 1.3～32.2, which means great difference and non-relativity between OHA and LHA. From the research on the enzyme from Bacillus circulans, we can find that OHA and LHA are enhanced by the addition of Na+ and K+ at different rates, Mg2+ activates OHA but inhibits LHA. The responses of ONPG and lactose to the enzyme activity are different as the function of temperature and pH. In a certain reaction system, the change of OHA/LHA value is not consistent with reaction conditions, thus a great influence on the actual applications of the enzyme will be caused if we estimate LHA using OHA.