THE DIVERSITY OF THE CATALYTIC PROPERTIES OF CLASS-A BETA-LACTAMASES
THE DIVERSITY OF THE CATALYTIC PROPERTIES OF CLASS-A BETA-LACTAMASES
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DOI：
10.1042/bj2650131
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发表时间：
1990-01-01
影响因子：
4.1
通讯作者：
FRERE, JM
中科院分区：
文献类型：
--
作者：
MATAGNE, A;MISSELYNBAUDUIN, AM;FRERE, JM
四种A类β-用24种不同底物研究了内酰胺酶。它们表现出广泛的变化。同样，氨基酸序列也有很大不同。然而，没有发现序列相似性和底物分布之间的关系。用含有大的空间位阻侧链的各种化合物观察到滞后和爆发。作为一个组，这些酶可以与C β-根据几种底物，特别是苯唑西林、氯唑西林和羧苄西林的kcat值，令人惊讶的是，用kcat/Km值进行这种区分是不可能的，kcat/Km值代表活性位点丝氨酸残基被β-丝氨酸酰化的速率。内酰胺。对于几种头孢菌素底物（例如头孢呋辛和头孢噻肟），A类酶始终表现出比C类酶更高的kcat值，因此掩盖了“青霉素酶"和”头孢菌素酶“之间的通常区别。A β类的再分配问题-将内酰胺酶分成亚类进行了讨论。
The catalytic properties of four class A .beta.-lactamases were studied with 24 differnt substrates. They exhibit a wide range of variation. Similarly, the amino acid sequences are also quite different. However, no relationships were found between the sequence similarities and the substrate profiles. Lags and bursts were observed with various compounds containing a large sterically hindered side chain. As a group, the enzyms could be distinguished from the class C .beta.-lactamase on the basis ofthe kcat, values for several substrates, particularly oxacillin, cloxacillin and carbenicillin. Surprisingly, that distinction was impossible with the kcat/Km values, which represent the rates of acylation of the active-site serine residue by the .beta.-lactam. For several cephalosporin substrates (e.g. cefuroxime and cefotaxime) class A enzymes consistently exhibited higher kcat values than class C enzymes, thus belying the usual distinction between ''penicillinases'' and ''cephalosporinases''. The problem of the repartition of class A .beta.-lactamases into sub-classes is discussed.