tetrahydropteroylglutamate methyltransferase; methionine-homocysteine methyltransferase; an enzyme that catalyzes the reaction of N5-methyltetrahydrofolate with l-homocysteine to form tetrahydrofolate and l-methionine; a cobalamin-requiring enzyme; a deficiency of this enzyme results in an accumulation of l-homocysteine and neurological abnormalities. SYN: tetrahydrofolate methyltransferase.