Boudet A M, Lécussan R, Boudet A
Enzymologie et Métabolisme, Equipe de Recherche associée au CNRS, Université Paul Sabatier-Centre de Physiologie Végétale, 118, route de Narbonne, F-31077, Toulase Cédex, France.
Planta. 1975 Jan;124(1):67-75. doi: 10.1007/BF00390069.
Two dehydroquinate hydro-lyases (E.C. 4.2.1.10) have been routinely separated from different organs of Zea mays L. by chromatography on Cellex-D Bio-Rad or hydroxypatite using linear salt gradients. Dehydroquinate hydro-lyase 1 is associated with shikimate: NADP(+) oxidoreductase (E.C. 1.1.1.25). DHQase 2 is a free constitutive enzyme; in this respect it differs from the inducible enzyme of microorganisms which appears only when dehydroquinate or quinate is the principal carbon source. DHQase 1 and DHQase 2 have a similar apparent Michaelis constant and pH optimum, but they differ in their molecular weight, thermal stability and sensitivity to metabolic effectors. DHQase 2 is specifically activated by shikimic acid. This strong activation and the channeling properties of the complex involved in the shikimate pathway can provide an effective means of control in the utilization of dehydroquinate between two different pathways. The significance of such a system involving both a specific regulation of isoenzymes and a molecular compartmentation by means of an enzymatic complex is discussed.
通过使用线性盐梯度在Cellex-D Bio-Rad或羟基磷灰石上进行色谱分离，已常规地从玉米（Zea mays L.）的不同器官中分离出两种脱氢奎尼酸水解酶（E.C. 4.2.1.10）。脱氢奎尼酸水解酶1与莽草酸：NADP(+)氧化还原酶（E.C. 1.1.1.25）相关联。脱氢奎尼酸水解酶2是一种游离的组成型酶；在这方面，它与仅在脱氢奎尼酸或奎尼酸作为主要碳源时才出现的微生物诱导酶不同。脱氢奎尼酸水解酶1和脱氢奎尼酸水解酶2具有相似的表观米氏常数和最适pH，但它们在分子量、热稳定性和对代谢效应物的敏感性方面存在差异。脱氢奎尼酸水解酶2被莽草酸特异性激活。这种强烈的激活以及莽草酸途径中所涉及复合物的通道化特性，可以为在两条不同途径之间利用脱氢奎尼酸提供一种有效的控制手段。本文讨论了这样一个涉及同工酶特异性调节和通过酶复合物进行分子分隔的系统的意义。
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