Activity of 3-Ketosteroid 9α-Hydroxylase (KshAB) Indicates Cholesterol Side Chain and Ring Degradation Occur Simultaneously in Mycobacterium tuberculosis
作者:Jenna K. Capyk、Israël Casabon、Robert Gruninger、Natalie C. Strynadka、Lindsay D. Eltis
DOI:10.1074/jbc.m111.289975
日期:2011.11
active site channel and could contribute to substrate specificity. These results indicate that the physiological substrates of KshAB are CoA thioester intermediates of cholesterol side chain degradation and that side chain and ring degradation occur concurrently in Mtb. This finding has implications for steroid metabolites potentially released by the pathogen during infection and for the design of inhibitors
结核分枝杆菌 (Mtb) 是一种重要的全球病原体,含有胆固醇分解代谢途径。尽管胆固醇分解代谢在 Mtb 中的确切作用仍不清楚,但该途径中的 Rieske 单加氧酶,3-酮类固醇 9α-羟化酶 (KshAB),已被确定为毒力因子。为了研究 KshAB 的生理底物,使用红球菌酰基辅酶 A 合成酶生产两种胆固醇衍生物的辅酶 A 硫酯:3-oxo-23,24-bisnorchol-4-en-22-oic acid(形成 4-BNC -CoA) 和 3-oxo-23,24-bisnorchola-1,4-dien-22-oic 酸(形成 1,4-BNC-CoA)。KshAB 对 CoA 硫酯底物的表观特异性常数 (k(cat)/K(m)) 是相应的 17-酮化合物先前提出的生理底物的 20-30 倍。在存在 1,4-BNC-CoA 的情况下,明显的 K(m)(O(2)) 为 90 + /-10 mu