细胞色素P450(P450,CYP)19A1是类固醇芳香化酶,负责雄激素(雄烯二酮或睾酮)向雌激素的三步转化的酶。最后一步是通过历史上有争议的反应机理进行的C-C键断裂(以甲酸形式除去19-氧代基团)。两种相互竞争的机制可能性涉及过氧化铁阴离子(Fe3O2-,化合物0)和过铁氧基物种(FeO3,化合物I)。辨别每种物种在反应中的作用的一种方法是使用氧-18标记,即,从18O2和H218O的反应产物甲酸。我们应用了这种方法,使用几个技术改进,为了研究19-氧代雄烯二酮被人P45019A1和一种新型的类固醇的变形,3-氧代萘烷-4-烯-10-甲醛(ODEC),兔P4502B4。两种醛底物都对非酶酸催化的脱甲酰化敏感,产生19-去甲类固醇,并建立了条件以避免人为生成甲酸的问题。化合物0反应途径占主导地位(即,Fe3O2-)在19-氧代雄烯二酮的P45019A1氧化和ODEC的P4502B4氧化中。P45019A1结果与我们先前的结论(J.Am.Chem.Soc.2014,136,15016-16025),归因于一些技术修改。
Cytochrome P450 (P450, CYP) 19A1 is the steroid aromatase, the enzyme responsible for the 3-step conversion of androgens (androstenedione or testosterone) to estrogens. The final step is C-C bond scission (removing the 19-oxo group as formic acid) that proceeds via a historically controversial reaction mechanism. The two competing mechanistic possibilities involve a ferric peroxide anion (Fe3+O2 -, Compound 0) and a perferryl oxy species (FeO3+, Compound I). One approach to discern the role of each species in the reaction is with the use of oxygen-18 labeling, i.e., from 18O2 and H2 18O of the reaction product formic acid. We applied this approach, using several technical improvements, to study the deformylation of 19-oxo-androstenedione by human P450 19A1 and of a model secosteroid, 3-oxodecaline-4-ene-10-carboxaldehyde (ODEC), by rabbit P450 2B4. Both aldehyde substrates were sensitive to non-enzymatic acid-catalyzed deformylation, yielding 19-norsteroids, and conditions were established to avoid issues with artifactual generation of formic acid. The Compound 0 reaction pathway predominated (i.e., Fe3+O2 -) in both P450 19A1 oxidation of 19-oxo-androstenedione and P450 2B4 oxidation of ODEC. The P450 19A1 results contrast with our prior conclusions (J. Am. Chem. Soc. 2014, 136, 15016-16025), attributed to several technical modifications.