A cytochrome P450 monooxygenase involved in primary bile acid biosynthesis. Catalyzes the 12alpha-hydroxylation of 7alpha-hydroxy-4-cholesten-3-one, an intermediate metabolite in cholic acid biosynthesis (PubMed:1400444, PubMed:8943286). Controls biliary balance of cholic acid and chenodeoxycholic acid, ultimately regulating the intestinal absorption of dietary lipids (By similarity). 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--hemoprotein reductase) (PubMed:1400444, PubMed:8943286). 7alpha-hydroxycholest-4-en-3-one + O2 + reduced [NADPH--hemoprotein reductase] = 7alpha,12alpha-dihydroxycholest-4-en-3-one + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] 5beta-cholestane-3alpha,7alpha-diol + O2 + reduced [NADPH--hemoprotein reductase] = 5beta-cholestane-3alpha,7alpha,12alpha-triol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] chenodeoxycholate + O2 + reduced [NADPH--hemoprotein reductase] = cholate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Up-regulated upon treatment with streptozotocin. Lipid metabolism; bile acid biosynthesis. Liver (at protein level). Belongs to the cytochrome P450 family.