Rotation of the <i>exo</i>-Methylene Group of (<i>R</i>)-3-Methylitaconate Catalyzed by Coenzyme B<sub>12</sub>-Dependent 2-Methyleneglutarate Mutase from <i>Eubacterium barkeri</i>
作者:Antonio J. Pierik、Daniele Ciceri、Gerd Bröker、Christopher H. Edwards、William McFarlane、Joachim Winter、Wolfgang Buckel、Bernard T. Golding
DOI:10.1021/ja020340f
日期:2002.11.1
possibilities for the mechanism of the carbon skeleton rearrangement of the substrate-derived radical to the product-related radical are considered. In both mechanisms an acrylate group migrates from C-3 of 2-methyleneglutarate to C-4. In the "addition-elimination" mechanism this 1,2-shift occurs via an intermediate, a 1-methylenecyclopropane-1,2-dicarboxylate radical, in which the migrating acrylate is simultaneously
来自厌氧真杆菌(梭状芽孢杆菌)barkeri 的 2-亚甲基戊二酸变位酶是一种腺苷钴胺素(辅酶 B(12))依赖性酶,可催化 2-亚甲基戊二酸与 (R)-3-甲基衣康酸的平衡。考虑了从底物衍生的自由基到产物相关自由基的碳骨架重排机制的两种可能性。在这两种机制中,丙烯酸酯基团从 2-亚甲基戊二酸的 C-3 迁移到 C-4。在“加成-消除”机制中,这种 1,2-转变通过中间体 1-亚甲基环丙烷-1,2-二羧酸酯基团发生,其中迁移的丙烯酸酯同时连接到 C-3 和 C-4。在“断裂-重组”机制中,迁移基团(一个 2-丙烯酰基自由基)在开始与 C-4 键合之前与 C-3 分离。为了区分这两种可能性,我们研究了 2-亚甲基戊二酸变位酶对立体特异性氘代底物 (Z)-3-甲基[2'-(2)H(1)]衣康酸酯和 (Z)-3 的作用-[2'-(2)H(1),methyl-(2)H(3)]甲基衣康酸酯。该酶催化两种化合物与其相应的