粗糙脉孢菌中可诱导的奎尼酸分解代谢途径中的一种酶——奎尼酸（莽草酸）脱氢酶的纯化与特性分析

Purification and characterization of quinate (shikimate) dehydrogenase, an enzyme in the inducible quinic acid catabolic pathway of Neurospora crassa.

作者信息

Barea J L, Giles N H

出版信息

Biochim Biophys Acta. 1978 May 11;524(1):1-14. doi: 10.1016/0005-2744(78)90097-9.

Abstract

The bifunctional enzyme quinate (shikimate) dehydrogenase (quinate: NAD+ oxidoreductase, EC 1.1.1.24), which catalyzes the first reaction in the inducible quinic acid catabolic pathway of Neurospora crassa, has been purified to homogeneity. The enzyme is a monomer of 41000 daltons with an s20,w = 2.94 S. However, electrophoresis under non-denaturing conditions revealed three protein species, which have both quinate and shikimate dehydrogenase activities. The enzyme, with a single binding site for both substrates, has a Km of 0.37 mM for quinate and of 1.18 mM for shikimate, although the V is about 3-fold higher with shikimate. Essential sulphydryl groups which were not localized in the active site were detected. Thermal stability of the enzyme was greatly enhanced by low concentrations of quinate, shikimate, NADH, or by high ionic strength.

摘要

双功能酶奎尼酸（莽草酸）脱氢酶（奎尼酸：NAD⁺氧化还原酶，EC 1.1.1.24）催化粗糙脉孢菌诱导型奎尼酸分解代谢途径中的第一步反应，已被纯化至同质。该酶是一种41000道尔顿的单体，s20,w = 2.94 S。然而，在非变性条件下进行的电泳显示有三种蛋白质，它们都具有奎尼酸和莽草酸脱氢酶活性。该酶对两种底物都有一个结合位点，对奎尼酸的Km为0.37 mM，对莽草酸的Km为1.18 mM，尽管以莽草酸为底物时V约高3倍。检测到了不在活性位点的必需巯基。低浓度的奎尼酸、莽草酸、NADH或高离子强度可大大提高该酶的热稳定性。