Major pathway of the conversion of propionyl-CoA into succinyl-CoA, which occurs in the mitochondria. The biotin-dependent enzyme PCC converts propionyl-CoA into d-methylmalonyl-CoA, which is then racemized by MCEE into l-methylmalonyl-CoA and isomerized by MMUT into succinyl-CoA, a citric acid cycle intermediate. MMUT requires the cofactor adenosylcobalamin, a vitamin B12 derivative, to be enzymatically active. MCEE, methylmalonyl-CoA epimerase; MMUT, methylmalonyl-CoA mutase; PCC, propionyl-CoA carboxylase.