Banerjee R, Vlasie M
Biochemistry Department, University of Nebraska, Lincoln, NE 68588-0664, USA.
Biochem Soc Trans. 2002 Aug;30(4):621-4. doi: 10.1042/bst0300621.
Adenosylcobalamin or coenzyme B(12)-dependent enzymes are members of the still relatively small group of radical enzymes and catalyse 1,2-rearrangement reactions. A member of this family is methylmalonyl-CoA mutase, which catalyses the isomerization of methylmalonyl-CoA to succinyl-CoA and, unlike the others, is present in both bacteria and animals. Enzymes that catalyse some of the most chemically challenging reactions are the ones that tend to deploy radical chemistry. The use of radical intermediates in an active site lined with amino acid side chains that threaten to extinguish the reaction by presenting alternative groups for abstraction poses the conundrum of how the enzymes control their reactivity. In this review, insights into this issue that have emerged from kinetic, mutagenesis and structural studies are described for methylmalonyl-CoA mutase.
腺苷钴胺素或辅酶B12依赖性酶是自由基酶中数量仍相对较少的一类成员，催化1,2-重排反应。该家族的一个成员是甲基丙二酰辅酶A变位酶，它催化甲基丙二酰辅酶A异构化为琥珀酰辅酶A，与其他成员不同的是，它在细菌和动物中都存在。催化一些化学上最具挑战性反应的酶往往采用自由基化学。在一个由氨基酸侧链排列的活性位点中使用自由基中间体，这些侧链有可能通过提供可供夺取的替代基团来终止反应，这就带来了酶如何控制其反应活性的难题。在这篇综述中，描述了从甲基丙二酰辅酶A变位酶的动力学、诱变和结构研究中得出的关于这个问题的见解。
