A cytochrome P450 monooxygenase involved in muricholic acid (MCA) synthesis (PubMed:27638959). Hydroxylates at the 6-beta position two major bile acids, chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA) to form alpha-MCA and beta-MCA, respectively (PubMed:27638959). May regulate NR1H4/farnesoid X receptor signaling, as taurine-conjugated MCAs are antagonists of NR1H4. 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) (PubMed:27638959). chenodeoxycholate + O2 + reduced [NADPH--hemoprotein reductase] = alpha-muricholate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] O2 + reduced [NADPH--hemoprotein reductase] + ursodeoxycholate = beta-muricholate + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Expressed in liver. Belongs to the cytochrome P450 family.