該基因編碼的蛋白質催化5,10-亞甲基四氫葉酸轉化為5-甲基四氫葉酸酯，這是同型半胱氨酸再甲基化為蛋氨酸的共基質。該基因的遺傳變異影響對閉塞性血管病、神經管缺陷、結腸癌和急性白血病的易感性，該基因的突變與亞甲基四氫葉酸還原酶缺乏有關。
The protein encoded by this gene catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. Genetic variation in this gene influences susceptibility to occlusive vascular disease, neural tube defects, colon cancer and acute leukemia, and mutations in this gene are associated with methylenetetrahydrofolate reductase deficiency.