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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]
In studies of human recombinant MTHFR, the protein encoded by 1298C cannot be distinguished from 1298A in terms of activity, thermolability, FAD release, or the protective effect of 5-methyl-THF. [22] The C mutation does not appear to affect the MTHFR protein. It does not result in thermolabile MTHFR and does not appear to affect homocysteine ...
[35] [36] Methionine synthase reductase (MTRR) or methylene-tetrahydrofolate reductase (MTHFR) deficiencies can also result in the condition. Most cases of methionine synthase deficiency are symptomatic within 2 years of birth with many patients rapidly developing severe encephalopathy. [37]
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.
THF is the immediate acceptor of one carbon unit for the synthesis of thymidine-DNA, purines (RNA and DNA) and methionine. The un-methylated form, folic acid (vitamin B 9 ), is a synthetic form of folate , and must undergo enzymatic reduction by dihydrofolate reductase ( DHFR ) to become biologically active.
[6] [7] [8] Furthermore, secondary cerebral folate deficiency can develop in patients with other conditions. For example, it can develop in AADC deficiency through the depletion of methyl donors, such as SAM and 5-MTHF, by O-methylation of the excessive amounts of L-dopa present in patients. [14] [15]
Folate deficiency can be secondary to vitamin B 12 deficiency or a defect in homocysteine methyl transferase that leads to a "folate trap" in which is an inactive metabolite that cannot be recovered. [1] Diagnosis is typically confirmed by blood tests, including a complete blood count, and serum folate levels. [1]
Methyl B 12: This form of vitamin B 12 is essential for conversion of Methy-THF (methyl tetrahydrofolate) into THF, and methyl (CH 3). The methyl group is then used to add carbon, to homocysteine, converting it into methionine. Methionine is further converted to S-adenosyl methionine, which in turn gives of the extra carbon it received from THF ...