REEXAMINATION OF THE ROLE OF ASP20 IN CATALYSIS BY BACTERIOPHAGE-T4 LYSOZYME
REEXAMINATION OF THE ROLE OF ASP20 IN CATALYSIS BY BACTERIOPHAGE-T4 LYSOZYME
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DOI：
10.1021/bi00103a010
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发表时间：
1991-10-01
期刊：
影响因子：
2.9
通讯作者：
POTEETE, AR
中科院分区：
文献类型：
--
作者：
HARDY, LW;POTEETE, AR
用半胱氨酸取代T4溶菌酶中的Asp 20产生了一种变体，该变体具有（1）接近野生型的比活性，（2）新获得的对巯基修饰试剂的敏感性，以及（3）与野生型酶非常相似的pH-活性曲线。 这些结果表明，在位置20的残基具有显着的亲核功能，而不仅仅是静电的作用。 溶菌酶催化作用的中间体可能是一种共价糖基酶，而不是最初提出的离子对。
Replacement of Asp20 in T4 lysozyme by Cys produces a variant with (1) nearly wild-type specific activity, (2) a newly acquired sensitivity to thiol-modifying reagents, and (3) a pH-activity profile that is very similar to that of the wild-type enzyme. These results indicate that the residue at position 20 has a significant nucleophilic function rather than merely an electrostatic role. The intermediate in catalysis by lysozyme is probably a covalent glycosyl-enzyme instead of the ion pair originally proposed.