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Methylenetetrahydrofolate reductase deficiency is the most common genetic cause of elevated serum levels of homocysteine (hyperhomocysteinemia). It is caused by genetic defects in MTHFR, which is an important enzyme in the methyl cycle. [1] Common variants of MTHFR deficiency are asymptomatic and have only minor effects on disease risk. [2]
Methylenetetrahydrofolate reductase (MTHFR) is the rate-limiting enzyme in the methyl cycle, and it is encoded by the MTHFR gene. [5] Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate , a cosubstrate for homocysteine remethylation to methionine .
5,10-Methylenetetrahydrofolate (N5,N10-Methylenetetrahydrofolate; 5,10-CH 2-THF) is cofactor in several biochemical reactions. It exists in nature as the diastereoisomer [6R]-5,10-methylene-THF. As an intermediate in one-carbon metabolism, 5,10-CH 2 -THF converts to 5-methyltetrahydrofolate , 5-formyltetrahydrofolate , and methenyltetrahydrofolate.
In enzymology, a methylenetetrahydrofolate reductase (ferredoxin) (EC 1.5.7.1) is an enzyme that catalyzes the chemical reaction 5-methyltetrahydrofolate + 2 oxidized ferredoxin ⇌ {\displaystyle \rightleftharpoons } 5,10-methylenetetrahydrofolate + 2 reduced ferredoxin + 2 H +
The following is a partial list of the "D" codes for Medical Subject Headings (MeSH), as defined by the United States National Library of Medicine (NLM). This list continues the information at List of MeSH codes (D12.644). Codes following these are found at List of MeSH codes (D13). For other MeSH codes, see List of MeSH codes.
It is produced from 5,10-methylenetetrahydrofolate by either a NAD+ dependent methylenetetrahydrofolate dehydrogenase, or a NADP+ dependent dehydrogenase. [1] It can also be produced as an intermediate in histidine catabolism, by formiminotransferase cyclodeaminase , from 5-formiminotetrahydrofolate .
In humans, tetrahydrofolic acid is produced from dihydrofolic acid by dihydrofolate reductase. This reaction is inhibited by methotrexate. [1] It is converted into 5,10-methylenetetrahydrofolate by serine hydroxymethyltransferase. Many bacteria produce tetrahydrofolic acid via dihydropteroate.
In enzymology, a methylenetetrahydrofolate-tRNA-(uracil-5-)-methyltransferase (EC 2.1.1.74) is an enzyme that catalyzes the chemical reaction 5,10-methylenetetrahydrofolate + tRNA containing uridine at position 54 + FADH 2 ⇌ {\displaystyle \rightleftharpoons } tetrahydrofolate + tRNA containing ribothymidine at position 54 + FAD