Vitamin B12 functions as a coenzyme for which of the following enzymes?

Explanation

Vitamin B12 serves as a coenzyme specifically for homocysteine methyltransferase, an enzyme involved in the methylation of homocysteine to methionine. It does not act as a coenzyme for isocitrate dehydrogenase, glycogen synthase, or glucose-6-phosphate dehydrogenase.