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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Insights into the structural basis of substrate recognition by histidinol-phosphate aminotransferase from Corynebacterium glutamicum.
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Insights into the structural basis of substrate recognition by histidinol-phosphate aminotransferase from Corynebacterium glutamicum.

机译：洞察基质的结构基础认识到histidinol-phosphate转氨酶的棒状杆菌glutamicum。

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摘要

Histidinol-phosphate aminotransferase (HisC) is a pyridoxal 5'-phosphate-dependent enzyme that catalyzes the reversible transamination reaction between histidinol phosphate (His-P) and 2-oxoglutarate (O-Glu). The crystal structures of apo histidinol-phosphate aminotransferase from Corynebacterium glutamicum, of the internal PLP aldimine adduct and of a pyridoxamine 5-phosphate-enzyme complex were determined at resolutions of 2.2, 2.1 and 1.8 A, respectively. Residues important for substrate specificity were identified by modelling His-P into the active site and comparison with crystal structures of HisC from Thermotoga maritima and Escherichia coli. Four of the residues lining the substrate-binding pocket were studied by site-directed mutagenesis. Kinetic analysis of the Tyr21Phe mutant suggested that the hydrogen bond between the side chain of this residue and the phosphate group of His-P is important for recognition of the natural substrate and discrimination against other potential amino donors suchas phenylalanine and leucine. The mutagenesis studies further indicated that residue Asn99 does not contribute to the specific recognition of the amino-acid donor, but may be involved in binding of the phosphate group of pyridoxal 5'-phosphate. The conserved residues Tyr123 and Tyr257 interact with the substrate through van der Waals interactions and their potential for hydrogen-bonding interactions is not utilized in substrate recognition, as the corresponding phenylalanine mutants show only a moderate effect on the catalytic efficiency kcat/Km.
机译：Histidinol-phosphate转氨酶(HisC)吡哆醛5 ' -phosphate-dependent酶催化反应可逆转氨作用histidinol磷酸盐(自己)和之间2-oxoglutarate (O-Glu)。apo histidinol-phosphate转氨酶从棒状杆菌属glutamicum,内部PLP醛亚胺加合物和维生素b65-phosphate-enzyme复杂的测定分辨率为2.2、2.1和1.8,分别。残留的重要底物特异性被造型自己活跃网站的晶体结构和比较从Thermotoga HisC maritima和大肠杆菌。substrate-binding口袋里进行了研究定点诱变。Tyr21Phe变异表明,氢侧链的残渣和之间的债券磷酸基的自己是很重要的自然基质和识别歧视其他潜在的氨基酸捐助者如苯丙氨酸和亮氨酸。诱变的研究进一步表明,残留Asn99并不具体识别氨基酸的捐赠者,但可能参与磷酸基的绑定5 '磷酸吡哆醛。Tyr123和Tyr257与基质交互通过范德华相互作用和他们的潜在的氢键相互作用在底物识别,不利用相应的苯丙氨酸突变体只显示一个温和的对催化效率的影响kcat /公里。

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