Bijault C, Dehennin L
Fondation de Recherche en Hormonologie, Fresnes, France.
J Steroid Biochem Mol Biol. 1991 Feb;38(2):165-72. doi: 10.1016/0960-0760(91)90122-l.
Steroid 21-hydroxylase activity of the microsome-enriched fraction of follicular linings from equine ovaries has been demonstrated by gas chromatography-mass spectrometry. The 21-hydroxylated metabolites were quantified by isotope dilution with deuterated analogues. The two most abundant potential substrates for follicular steroid 21-hydroxylase, progesterone (P) and 17-hydroxyprogesterone (17OHP), were converted respectively to 11-deoxycorticosterone (DOC) and 11-deoxycortisol with corresponding apparent specific activities of 308 and 24 pmol/mg protein/h and apparent Km values of 1.1 and 6.4 microM. Competitive inhibition of the P-to-DOC conversion was exerted by 17OHP and pregnenolone. Hence, the ovarian follicle of the mare is an extraadrenal site of preferential DOC biosynthesis by an enzyme having steroid 21-hydroxylase activity.
气相色谱-质谱法已证实马卵巢卵泡内膜富含微粒体部分的类固醇21-羟化酶活性。通过用氘代类似物进行同位素稀释对21-羟化代谢物进行定量。卵泡类固醇21-羟化酶的两种最丰富的潜在底物，孕酮（P）和17-羟孕酮（17OHP），分别转化为11-脱氧皮质酮（DOC）和11-脱氧皮质醇，相应的表观比活性分别为308和24 pmol/mg蛋白/小时，表观Km值分别为1.1和6.4 microM。17OHP和孕烯醇酮对P向DOC的转化有竞争性抑制作用。因此，母马的卵巢卵泡是具有类固醇21-羟化酶活性的酶优先生物合成DOC的肾上腺外部位。
