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Structural and catalytic diversity within the amidohydrolase superfamily

机译：酰胺水解酶超家族中的结构和催化多样性

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摘要

The amidohydrolase superfamily comprises a remarkable set of enzymes that catalyze the hydrolysis of a wide range of substrates bearing amide or ester functional groups at carbon and phosphorus centers. The most salient structural landmark for this family of hydrolytic enzymes is a mononuclear or binuclear metal center embedded within the confines of a (beta/alpha)(8)-barrel structural fold. Seven variations in the identity of the specific amino acids that function as the direct metal ligands have been structurally characterized by X-ray crystallography. The metal center in this enzyme superfamily has a dual functionality in the expression of the overall catalytic activity. The scissile bond of the substrate must be activated for bond cleavage, and the hydrolytic water molecule must be deprotonated for nucleophilic attack. In all cases, the nucleophilic water molecule is activated through complexation with a mononuclear or binuclear metal center. In the binuclear metal centers, the carbonyl and phosphoryl groups of the substrates are polarized through Lewis acid catalysis via complexation with the beta-metal ion, while the hydrolytic water molecule is activated for nucleophilic attack by interaction with the cc-metal ion. In the mononuclear metal centers, the substrate is activated by proton transfer from the active site, and the water is activated by metal ligation and general base catalysis. The substrate diversity is dictated by the conformational restrictions imposed by the eight loops that extend from the ends of the eight P-strands.
机译：酰胺水解酶超家族包括一组杰出的酶，它们催化在碳和磷中心带有酰胺或酯官能团的多种底物的水解。该水解酶家族最显着的结构标志是嵌入（beta / alpha）（8）-桶状结构折叠区域内的单核或双核金属中心。通过X射线晶体学在结构上表征了用作直接金属配体的特定氨基酸的身份的七个变化。该酶超家族中的金属中心在总体催化活性的表达中具有双重功能。底物的易裂键必须被激活才能进行键裂解，而水解水分子必须被去质子化才能发生亲核攻击。在所有情况下，亲核水分子都通过与单核或双核金属中心络合而活化。在双核金属中心，底物的羰基和磷酰基通过与β-金属离子络合的路易斯酸催化而极化，而水解水分子则通过与cc-金属离子的相互作用而被激活进行亲核攻击。在单核金属中心，底物通过质子从活性位点转移而被激活，水通过金属连接和一般的碱催化而被激活。底物多样性是由从八个P链末端延伸的八个环所施加的构象限制所决定的。

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