Conversion of 7-Dehydrocholesterol to 7-Ketocholesterol Is Catalyzed by Human Cytochrome P450 7A1 and Occurs by Direct Oxidation without an Epoxide Intermediate
作者:Raku Shinkyo、Libin Xu、Keri A. Tallman、Qian Cheng、Ned A. Porter、F. Peter Guengerich
DOI:10.1074/jbc.m111.282434
日期:2011.9
this compound have been identified, with cholesterol being the presumed precursor. Although routes for formation of the 7-keto compound from cholesterol have been established, we found that 7-dehydrocholesterol (the immediate precursor of cholesterol) is oxidized by P450 7A1 to 7-ketocholesterol (k(cat)/K(m) = 3 x 10(4) m(-1) s(-1)). P450 7A1 converted lathosterol (Delta(5)-dihydro-7-dehydrocholesterol)
7-Ketocholesterol 是一种生物活性甾醇,是一种有效的细胞色素 P450 7A1 竞争性抑制剂,在肝细胞中具有毒性。这种化合物的多种来源已被确定,胆固醇是推测的前体。尽管已经建立了从胆固醇形成 7-酮化合物的途径,但我们发现 7-脱氢胆固醇(胆固醇的直接前体)被 P450 7A1 氧化为 7-酮胆固醇(k(cat)/K(m) = 3 x 10(4) m(-1) s(-1))。P450 7A1 将 Lathosterol (Delta(5)-dihydro-7-dehydrocholesterol) 转化为 7-keto 和 7alpha,8alpha-epoxide 产物的混合物(~1:2 比例),环氧化物不会重排为酮。7-脱氢胆固醇的氧化主要形成7-酮胆固醇,7α,8α-环氧化物仅作为次要产物;合成的环氧化物在 P450 7A1 存在下是稳定的。7-脱氢胆固醇氧化为 7-酮胆固醇的机制被认为涉及