蜡样芽胞杆菌的晶体结构phosphonoacetaldehyde水解酶:洞察磷键裂解和催化多样化的催化酶总科。
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张莫莱斯MC,张W,贝克,G, Dunaway-Mariano D,艾伦KN
蜡样芽胞杆菌的晶体结构phosphonoacetaldehyde水解酶:洞察磷键裂解和催化多样化的催化酶总科。
生物化学。2000年8月29日,39 (34):10385 - 96。
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10956028 (在PubMed]
- 文摘
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Phosphonoacetaldehyde水解酶(phosphonatase)催化的水解Phosphonoacetaldehyde乙醛和磷酸盐的使用Mg (II)作为辅助因子。通过小说bicovalent催化机理反应所得的活性部位的亲核试剂提取磷酰基集团从中间形成席夫碱Lys53 phosphonoacetaldehyde。在这项研究中,蜡样芽胞杆菌的x射线晶体结构phosphonatase为包裹着的磷钨酸(产品)模拟(K (i) = 50 microM)和3.0毫克(II)代数余子式决心解决的(结晶)= 0.248和R(免费)= 0.284。每个单体是由一个α/β组成的核心领域集中位于six-stranded平行β褶板包围六阿尔法螺旋。两个灵活、溶剂化连接器连接到一个小型股域(残留21 - 99),由一个反平行的,five-helix包。subunit-subunit接口,由两alpha8螺旋对称包装从各自的核心领域,通过疏水效应来源于稳定Met171配对的反溶剂,Trp164, Tyr162, Tyr167, Tyr176侧链。的活性位点位于domain-domain接口每个亚基。帽上的席夫碱形成Lys53定位域而钨酸和Mg (II)绑定到核心领域。毫克(II)钨酸配体包括两个氧原子的配体,一个氧羧化物的Asp12 Asp186, Ala14的骨干羰基氧和水形成氢键的羧酸盐Asp190 Thr187。钨酸胍盐组Arg160结合亲核试剂Asp12提出,这是适当的定位为内联攻击钨原子。 The side chains of the core domain residue Tyr128 and the cap domain residues Cys22 and Lys53 are located nearby. The identity of Asp12 as the active-site nucleophile was further evidenced by the observed removal of catalytic activity resulting from Asp12Ala substitution. The similarity of backbone folds observed in phosphonatase and the 2-haloacid dehalogenase of the HAD enzyme superfamily indicated common ancestry. Superposition of the two structures revealed a conserved active-site scaffold having distinct catalytic stations. Analysis of the usage of polar amino acid residues at these stations by the dehalogenases, phosphonatases, phosphatases, and phosphomutases of the HAD superfamily suggests possible ways in which the active site of an ancient enzyme ancestor might have been diversified for catalysis of C-X, P-C, and P-O bond cleavage reactions.