Purification from adult pig testicular P-450 and 17 alpha-hydroxylase activity of P-450 containing liposomal membranes

A cytochrome P-450 from adult pig testicular microsomes was purified to a specific content of 12 nmol P-450/mg protein. P-450 has a minimum molecular weight of 46000 +/- 1000, as judged on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Adult testicular P-450 is prepared in the low-spin form with an absorbance maximum at 417 nm. The substrate-induced difference spectrum with progesterone is a typical I difference spectrum. P-450 was incorporated into liposomal membranes composed of phosphatidylcholine, and 17 alpha-hydroxylase activity was shown to amount to 15.5 nmol product/min/nmol of P-450. Furthermore, testicular cytochrome b 5 did not increase the 17 alpha-hydroxylase activity, and the activity was largely inhibited by the addition of sodium cholate, Emulgen 913 and testicular lipid.