Molecular cloning and characterization of Japanese eel ovarian P450c17 (CYP17) cDNA

As a first step in investigating the mechanism underlying the steroidogenic shift from the production of ovarian androgens (vitellogenic stage) to tha t of 17 alpha-hydroxylated progestins (maturational stage) in Japanese eel during induced oogenesis, a cDNA encoding Japanese eel (Anguilla japonica) ovarian P450c17 (CYP17: steroid 17 alpha-hydroxylase/C17-20 lyase) was clon ed and sequenced. This cDNA contained the complete coding region representi ng 510 amino acid residues, which showed high sequence homology to those of rainbow trout (74%) and mammals (45-55%). The protein encoded by this cDNA possessed high enzymatic activities of 17 alpha-hydroxylase and C17-20 lya se, thus quickly converting pregnenolone and progesterone to their respecti ve delta(4) and delta(5) C19 products. P450c17 produced a single transcript of 2.4 kb in length, as assessed by Northern blot. Transcript levels of th is enzyme significantly increased throughout artificially induced ovarian d evelopment. Considering this together with the previous data showing that C 17-20 lyase activity decreased from the vitellogenic to the maturational st age, whereas 17 alpha-hydroxylase activity increased, the present data sugg est that changes in C17-20 lyase activity (the production of androgens) do not depend on transcriptional changes of the P450c17gene. (C) 2000 Academic Press.