Vitamin B12 (methyl-Cobalamin) is important in the conversion of N5-methylTHF to THF. The conversion of N5-methyl-THF is important because THF is a cofactor for Homocysteine methyltransferase. Homocysteine methyltransferase is the enzyme that converts Homocysteine to methionine.

In Odd-chain fatty acid oxidation, the last three carbons of the chain are cofactored with the active form of panthotenic acid (CoA) to form propionyl CoA. Propionyl CoA is converted to methylmalonyl CoA. Methylmalonyl CoA reacts with methylmalonyl CoA mutase, with the help of Deoxyadenosyl cobalamin (Vitamin B12) to form succinyl CoA