A cytochrome P450 monooxygenase involved in corticoid and androgen biosynthesis. Catalyzes 17-alpha hydroxylation of C21 steroids, which is common for both pathways . A second oxidative step, required only for androgen synthesis, involves an acyl-carbon cleavage. Hydroxylates pregnenolone to form 17-alpha pregnenolone, followed by the cleavage of the C17-C20 bond to form dehydroepiandrosterone (DHEA) . Has 17-alpha hydroxylase activity toward progesterone . The 17-alpha hydroxy intermediates, as part of adrenal glucocorticoids biosynthesis pathway, are precursors of cortisol. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (CPR; NADPH-ferrihemoprotein reductase) (By similarity).
Subcellular locations: Endoplasmic reticulum membrane, Microsome membrane