Biosynthesis of 17α,20α‐dihydroxy‐4‐pregnen‐3‐one from 17α‐hydroxyprogesterone by spermatozoa of the common carp, <i>Cyprinus carpio</i>

Abstract

Abstract Isolated sperm of the common ( Cyprinus carpio ) were incubated with 4‐ 14 C‐labeled 17α‐hydroxyprogesterone at 22°C for 60 min; the medium was extracted, and the products were separated by thin‐layer chromatography (TLC). An autoradiogram of the TLC plate showed that a single major metabolite was produced, which had an Rf value lower than that of 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17α,20β‐diOHprog) but which was identical to that of its isomer, 17α,20α‐dihydroxy‐4‐pregnen‐3‐one (17α,20α‐diOHprog). The metabolite behaved identically on thin‐layer chromatograms to authentic 17α,20α‐diOHprog after both acetylation and oxidation, and had the same retention time as authentic 17α,20α‐diOHprog when separated by highperformance liquid chromatography (HPLC). The identity of the metabolite was confirmed by recrystallizing it to a constant specific activity after repeated crystallization with authentic 17α,20α‐diOHprog. These results indicate that the sperm cells of common carp contain the enzyme 20α‐hydroxysteroid dehydrogenase and have the capacity to produce high levels of 17α,20α‐diOHprog in the presence of 17α‐hydroxyprogesterone.