Eliot Andrew C, Kirsch Jack F
Department of Chemistry, University of California-Berkeley, Berkeley, California 94720-3206, USA.
Acc Chem Res. 2003 Oct;36(10):757-65. doi: 10.1021/ar0202767.
Enzymes are remarkable not only in their ability to enhance reaction rates, but also because they do so selectively, directing reactive intermediates toward only one of multiple potential products. 1-Aminocyclopropane-1-carboxylate (ACC) synthase and 7,8-diaminopelargonic acid synthase are pyridoxal 5'-phosphate-dependent enzymes that utilize S-adenosyl-l-methionine as a substrate but yield different products. The former produces ACC by alpha,gamma-elimination, while the latter makes S-adenosyl-4-methylthio-2-oxobutanoate by transamination. The mechanisms of these two reactions are the same up to the formation of a quinonoid intermediate, from which they diverge. This Account explores how the active-site topology of the enzyme-intermediate complexes decides this pathway bifurcation.
酶不仅因其提高反应速率的能力而引人注目，还因其具有选择性，能将反应中间体导向多种潜在产物中的一种。1-氨基环丙烷-1-羧酸（ACC）合酶和7,8-二氨基壬酸合酶是依赖于磷酸吡哆醛5'-磷酸的酶，它们以S-腺苷-L-甲硫氨酸为底物，但产生不同的产物。前者通过α,γ-消除反应生成ACC，而后者通过转氨作用生成S-腺苷-4-甲硫基-2-氧代丁酸。这两个反应的机制在形成醌型中间体之前是相同的，之后它们分道扬镳。本综述探讨了酶-中间体复合物的活性位点拓扑结构如何决定这种途径分支。
