The relation between two molecular species of P-450 in adult testis and 17 alpha-hydroxylase and 17,20-lyase activities.

Two P-450s from adult pig testis were purified to specific contents of 11.2 and 12.0 nmol P-450/mg protein and shown to have minimum molecular weights of 45,000 and 46,000, respectively. The absorption spectra were typical of P-450s. The P-450s were separated from the two fractions by CM-C50 Sephadex column chromatography. One P-450 (M(r) = 45000) exhibited 17,20-lyase activity of 6.78 nmol of androstenedione/min/nmol P-450, on incubation with 17 alpha-hydroxyprogesterone as a substrate. The other P-450 (M(r) = 46,000) exhibited no 17,20-lyase activity. Both P-450s exhibited 17 alpha-hydroxylase activity that amounted to 10 nmol of steroid products. Accordingly, the two molecular species of P-450 are thus markedly different in 17,20-lyase activity toward 17 alpha-hydroxyprogesterone.