§ Glossary · biology

MTHFR

Methylenetetrahydrofolate reductase — enzyme that activates folate; common variants reduce its efficiency.

MTHFR (methylenetetrahydrofolate reductase) is the enzyme that converts 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate (5-MTHF), the active form of folate used in methylation reactions including the conversion of homocysteine back to methionine. Two common polymorphisms — C677T and A1298C — reduce MTHFR enzyme activity. C677T homozygotes (~10% of European-descent populations) have ~30–40% normal MTHFR activity and are associated in the literature with elevated homocysteine, particularly when folate intake is inadequate. The standard clinical workaround is supplementing methylated folate (5-MTHF) directly.

Related
§ Related reading