A cytochrome P450 monooxygenase that plays a major role in adrenal steroidogenesis. Catalyzes the hydroxylation at C-21 of progesterone and 17alpha-hydroxyprogesterone to respectively form 11-deoxycorticosterone and 11-deoxycortisol, intermediate metabolites in the biosynthetic pathway of mineralocorticoids and glucocorticoids. 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). O2 + progesterone + reduced [NADPH--hemoprotein reductase] = 21-hydroxyprogesterone + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 17alpha-hydroxyprogesterone + O2 + reduced [NADPH--hemoprotein reductase] = 11-deoxycortisol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Expressed in the adrenal gland, kidney, aorta, liver, cerebellum, hypothalamus and brain stem. The leucine-rich hydrophobic amino acid N-terminal region probably helps to anchor the protein to the microsomal membrane. Belongs to the cytochrome P450 family.