Vitamin B12 acts as co-enzyme to which one of the following enzymes?

Vitamin B12 acts as co-enzyme to enzyme Homocysteine methyltransferase in the reaction <img src=" /> Folic acid deficiency may cause increased homocysteine levels in the blood. Plasma homocysteine levels above 15 micromoles / L is known to increase the risk of coronary aery diseases. Providing adequate doses of pyridoxine, B12, and folic acid may lower the homocysteine levels. Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 475, fig harper 44.14 page 558