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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >1.6 A structure of an NAD(+)-dependent quinate dehydrogenase from Corynebacterium glutamicum.
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1.6 A structure of an NAD(+)-dependent quinate dehydrogenase from Corynebacterium glutamicum.

机译：1.6 NAD(+)端依赖奎尼酸的结构脱氢酶从棒状杆菌glutamicum。

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To date, three different functional classes of bacterial shikimate/quinate dehydrogenases have been identified and are referred to as AroE, SDH-L and YdiB. The enzyme AroE and the catalytically much slower SDH-L clearly prefer NADP(+)/NADPH as the cosubstrate and are specific for (dehydro-)shikimate, whereas in YdiB the differences in affinity for NADP(+)/NADPH versus NAD(+)/NADH as well as for (dehydro-)shikimate versus (dehydro-)quinate are marginal. These three subclasses have a similar three-dimensional fold and hence all belong to the same structural class of proteins. In this paper, the crystal structure of an enzyme from Corynebacterium glutamicum is presented that clearly prefers NAD(+) as a cosubstrate and that demonstrates a higher catalytic efficiency for quinate rather than shikimate. While the kinetic constants for this enzyme clearly differ from those reported for AroE, SDH-L and YdiB, the three-dimensional structure of this protein is similar to members of these three subclasses. Thus, the enzyme described here belongs to a new functional class of the shikimate/quinate dehydrogenase family. The different substrate and cosubstrate specificities of this enzyme relative to all other known bacterial shikimate/quinate dehydrogenases are discussed by means of analyzing the crystal structure and derived models. It is proposed that in contrast to shikimate, quinate forms a hydrogen bond to the NAD(+). In addition, it is suggested that the hydroxyl group of a conserved active-site threonine hydrogen bonds to quinate more effectively than to shikimate. Also, the hydroxyl group of a conserved tyrosine approaches the carboxylate group of quinate more closely than it does the carboxylate group of shikimate. Taken together, these factors most likely lead to a lower Michaelis constant and therefore to a higher catalytic efficiency for quinate. The active site of the dehydrogenase reported here is larger than those of other known shikimate/quinate dehydrogenases, which may explain why quinate is easily accommodated within the catalytic cleft.
机译：迄今为止,三个不同功能的类细菌shikimate /奎尼酸脱氢酶被确认,被称为AroESDH-L YdiB。催化地SDH-L显然更喜欢慢得多辅酶ii (+) / NADPH作为辅被用物和具体(脱氢)shikimate,而在YdiB亲和力的差异为辅酶ii (+) / NADPH和NAD / NADH(+)和(脱氢)shikimate与(脱氢)奎尼酸是边际。三个子类也有类似的三维褶皱,因此都属于相同的结构类的蛋白质。棒状杆菌属的一种酶的结构glutamicum显然更喜欢了NAD(+)作为一个辅被用物,演示了一个奎尼酸,而较高的催化效率shikimate。这种酶明显不同于那些报道AroE SDH-L YdiB,三维这种蛋白质的结构类似于成员这三个子类。这里描述属于一个新的功能类shikimate /奎尼酸脱氢酶家族。不同的衬底和辅被用物相对于所有这种酶的特异性其他已知的细菌shikimate /奎尼酸通过讨论脱氢酶分析晶体结构和派生模型。shikimate,奎尼酸形成的氢键NAD(+)。羟基守恒的活性部位苏氨酸氢键奎尼酸更多有效shikimate。组的守恒的酪氨酸的方法奎尼酸的羧基比它更密切shikimate的羧基。在一起,这些因素很可能导致米氏常数,因此降低奎尼酸较高的催化效率。脱氢酶的活性部位是报道更大的比其他已知的shikimate /奎尼酸脱氢酶,这可能解释为什么奎尼酸很容易适应催化裂。

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