CYP17A1

CYP17A1 (also known as 17&alpha;-hydroxylase/17,20 lyase) is a cytochrome P450 enzyme which acts upon pregnenolone and progesterone to add a hydroxyl (-OH) group at carbon 17 of the steroid D ring (the hydroxylase activity), or acts upon 17-hydroxyprogesterone and 17-hydroxypregnenolone to split the side chain off the steroid nucleus (the lyase activity).