Promiscuous partitioning of a covalent intermediate common in the pentein superfamily
Promiscuous partitioning of a covalent intermediate common in the pentein superfamily
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DOI：
10.1016/j.chembiol.2008.03.012
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发表时间：
2008-05-01
影响因子：
--
通讯作者：
Fast, Walter
中科院分区：
文献类型：
--
作者：
Linsky, Thomas W.;Monzingo, Arthur F.;Fast, Walter
五肽超家族中的许多酶在其催化机制中使用瞬时共价中间体。在这里，我们捕获和确定一个稳定的共价加合物的结构，模仿这个中间体使用突变体二甲基精氨酸二甲氨基水解酶和替代底物。观察到的酶和捕获的加合物之间的相互作用表明正常催化的第一和第二半反应的亲核试剂之间的攻角改变。稳定的共价加合物还能够进一步反应。加入咪唑可恢复原有的水解活性。值得注意的是，添加其他胺反而产生取代的精氨酸产物，其产生于中间体分配到进化相关的脒基转移酶反应途径中。该酶为脒基转移酶反应提供了选择性和催化作用，强调了这种机械多样性酶超家族中反应途径的共性。这种中间体的混杂分配也可能有助于阐明这些酶的进化历史。
Many enzymes in the pentein superfamily use a transient covalent intermediate in their catalytic mechanisms. Here we trap and determine the structure of a stable covalent adduct that mimics this intermediate using a mutant dimethylarginine dimethylaminohydrolase and an alternative substrate. The interactions observed between the enzyme and trapped adduct suggest an altered angle of attack between the nucleophiles of the first and second half-reactions of normal catalysis. The stable covalent adduct is also capable of further reaction. Addition of imidazole rescues the original hydrolytic activity. Notably, addition of other amines instead yields substituted arginine products, which arise from partitioning of the intermediate into the evolutionarily related amidinotransferase reaction pathway. The enzyme provides both selectivity and catalysis for the amidinotransferase reaction, underscoring commonalities among the reaction pathways in this mechanistically diverse enzyme superfamily. The promiscuous partitioning of this intermediate may also help to illuminate the evolutionary history of these enzymes.