Mechanism-Based Cofactor Derivatization of a Copper Amine Oxidase by a Branched Primary Amine Recruits the Oxidase Activity of the Enzyme to Turn Inactivator into Substrate
作者:Chunhua Qiao、Ke-Qing Ling、Eric M. Shepard、David M. Dooley、Lawrence M. Sayre
DOI:10.1021/ja058838f
日期:2006.5.1
to a transamination mechanism. Following the initial isomerization of substrate Schiff base to product Schiff base, a facile aromatization of the latter results in a metastable N-aryl derivative of the reduced cofactor aminoresorcinol, which is catalytically inactive. The latter derivative is then slowly oxidized by O(2), apparently facilitated partially by the active-site Cu(II), to form a quinonimine
铜胺氧化酶 (CAO) 已进化为催化未支化的伯胺氧化脱氨基为醛。我们报告了带有芳香化倾向部分的支链伯胺 4-amino-4,5-dihydrothiophene-2-carboxylate (1),被牛血浆胺氧化酶 (BPAO) 对映选择性识别 (S >> R)作为临时灭活剂和底物。底物活性源于 O(2) 依赖的共价修饰酶的营业额,释放 4-aminothiophene-2-carboxylate (2) 作为最终产品。(S)-1 与 BPAO 的相互作用发生在酶活性位点内,解离常数为 0.76 microM。来自动力学和光谱研究的证据,以及 BPAO 与 (S)-1 的化学计量反应的 HPLC 分析,结合使用醌辅因子模拟物的模型研究,确定酶根据转氨机制代谢 1。在底物席夫碱初始异构化为席夫碱产物后,后者的轻松芳构化导致还原的辅因子氨基间苯二酚的亚稳态 N-芳基衍生物,其无催化活性。后一种衍生物随后被