大肠杆菌PdxA的晶体结构,参与磷酸吡哆醛的酶生物合成途径。
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李Sivaraman J, Y,银行J,甘蔗,哑光,Cygler M
大肠杆菌PdxA的晶体结构,参与磷酸吡哆醛的酶生物合成途径。
J生物化学杂志。2003年10月31日,278 (44):43682 - 90。Epub 2003 8月1。
- PubMed ID
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12896974 (在PubMed]
- 文摘
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5 '磷酸吡哆醛是一个重要的辅助因子对许多酶负责氨基酸的代谢转换。两条途径的从头合成是已知的。途径利用大肠杆菌由6个酶步骤由六种不同的酶催化的。第四步是由4-hydroxythreonine-4-phosphate催化脱氢酶(PdxA,提到过1.1.1.262),把4-hydroxy-l-threonine磷酸(HTP) 3-amino-2-oxopropyl磷酸盐。这个二价金属ion-dependent酶有严格要求的磷酸酯形式衬底HTP,但可以利用NADP +或NAD +氧化还原代数余子式我们报告大肠杆菌PdxA及其复杂的晶体结构和HTP Zn2 +。蛋白质形成紧密地绑定二聚体。每个单体都有一个α/β/ alpha-fold和可分为两个子域。活性位点位于二聚体界面,在两个子域之间的间隙和涉及单体残留。Zn2 +离子是绑定在每个活跃的网站,协调由三个守恒的组氨酸残基单体。 In addition two conserved amino acids, Asp247 and Asp267, play a role in maintaining integrity of the active site. The substrate is anchored to the enzyme by the interactions of its phospho group and by coordination of the amino and hydroxyl groups by the Zn2+ ion. PdxA is structurally similar to, but limited in sequence similarity with isocitrate dehydrogenase and isopropylmalate dehydrogenase. These structural similarities and the comparison with a NADP-bound isocitrate dehydrogenase suggest that the cofactor binding mode of PdxA is very similar to that of the other two enzymes and that PdxA catalyzes a stepwise oxidative decarboxylation of the substrate HTP.