菜心溶菌酶的提纯及酶学性质

Purification and Enzymatic Properties of the Lysozyme from Brassica campestris L. ssp. chinensis var. utilis

菜心（ＢｒａｓｓｉｃａｃａｍｐｅｓｔｒｉｓＬ．ｓｓｐ．ｃｈｉｎｅｎｓｉｓｖａｒ．ｕｔｉｌｉｓ）叶子高速捣碎后，滤液经酸碱处理，硫酸铵分步沉淀，凝胶柱层析等步骤分离纯化溶菌酶，酶比活力达３４１４．６Ｕ／ｍｇ，纯化倍数为１９７．４。菜心溶菌酶在较宽的温度或ｐＨ值范围均有活性，最适温度为６０℃，最适ｐＨ值为５．８，底物Ｋｍ值为８７μｇ／ｍＬ。该酶对热和酸碱的稳定性较高，巯基和酪氨酸残基不是该酶活性中心的必需基团。

Lysozyme was purified from the leaf homogenate of Brassica campestris L. ssp.chinensis var. utilis by the procedures of heat processing,pH alternative precipitation, ammonium sulfate differentiate precipitation, Sephadex G-75 and SP-Sephadex C-50 column chromatography. Compared with the crude extract, the resulting enzyme solution was purified by 197. 4 folds, and its specific activity was 3414. 6 units/mg. The enzymatic properties of the lysozyme was tested by using M. lysodeikticus as a substrate. As a result, the optimum temperature is 60℃,the optimum PH is 5. 8 and the Km value is 87Ag/mL. It is quite stable in a wide range of temperature or PH. The enzyme activity was not affected by p-chloromercuribenzoic acid, iodoacetic acid, and N-bromosuccinimide, so it is considered that sulfhydryl and tyrosine residues are not present at its active site.