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拜氏固氮菌乙酰乙酰辅酶A还原酶的纯化与特性分析

The purification and characterization of acetoacetyl-coenzyme A reductase from Azotobacter beijerinckii.

作者信息

Ritchie G A, Senior P J, Dawes E A

出版信息

Biochem J. 1971 Jan;121(2):309-16. doi: 10.1042/bj1210309.

Abstract

A soluble acetoacetyl-CoA reductase (EC 1.1.1.36) was purified 54-fold from Azotobacter beijerinckii N.C.I.B. 9067 and the reaction product identified as d(-)-beta-hydroxybutyryl-CoA. The Michaelis constants for acetoacetyl-CoA, NADPH and NADH were determined and the reaction rate was found to be some fivefold greater with NADPH than with NADH. At neutral pH the equilibrium greatly favours the formation of the reduced product. Substrate specificity was in the order: acetoacetyl-CoA>acetoacetylpantetheine>acetoacetyl-(acyl-carrier protein). The enzyme possesses a functional thiol group, suffers inactivation by oxygen and is inhibited by thiol-blocking reagents. Inhibition by p-chloromercuribenzoate is reversed by excess of dithiothreitol, which also protects the enzyme from inactivation by oxygen.

摘要

从拜氏固氮菌N.C.I.B. 9067中纯化出一种可溶性乙酰乙酰辅酶A还原酶(EC 1.1.1.36),纯化倍数为54倍,反应产物鉴定为d(-)-β-羟基丁酰辅酶A。测定了该酶对乙酰乙酰辅酶A、NADPH和NADH的米氏常数,发现其对NADPH的反应速率比对NADH的反应速率大约高五倍。在中性pH条件下,平衡极大地有利于还原产物的形成。底物特异性顺序为:乙酰乙酰辅酶A>乙酰乙酰泛酰巯基乙胺>乙酰乙酰-(酰基载体蛋白)。该酶具有一个功能性巯基,会被氧气灭活,并受到巯基阻断试剂的抑制。对氯汞苯甲酸的抑制作用可被过量的二硫苏糖醇逆转,二硫苏糖醇还能保护该酶不被氧气灭活。

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