Methyl folate trap is due to methionine synthase defect
The “methyl folate trap” refers to a condition in which methyl folate (5-methyltetrahydrofolate), a form of folate involved in the transfer of one-carbon units in various metabolic reactions, becomes sequestered and unavailable for other essential reactions. This can occur when there’s a defect in the enzyme methylenetetrahydrofolate reductase (MTHFR).
However, the methyl folate trap is not specifically due to a defect in methionine synthase. Instead, it’s associated with the impaired conversion of methyl folate to tetrahydrofolate (THF) by MTHFR. This enzyme catalyzes the conversion of 5-methyltetrahydrofolate to tetrahydrofolate, which is essential for the synthesis of thymidine, purines, and other molecules.
When MTHFR activity is reduced, as can happen with certain genetic variants or nutritional deficiencies, the conversion of methyl folate to THF is impaired. This leads to an accumulation of methyl folate and a decrease in available THF. As a result, the one-carbon units required for reactions such as the remethylation of homocysteine to methionine (catalyzed by methionine synthase) become limited, contributing to elevated levels of homocysteine and decreased methionine synthesis.
Methionine synthase is another key enzyme in folate metabolism, and its deficiency or dysfunction can lead to a separate set of metabolic disturbances, including impaired DNA synthesis, abnormal methylation reactions, and neurological complications associated with methylcobalamin (vitamin B12) deficiency.
In summary, while methionine synthase deficiency can contribute to methyl folate trap indirectly by impairing the remethylation of homocysteine, the primary cause of the methyl folate trap is often attributed to defects in MTHFR. Both enzymes play critical roles in folate metabolism, and disruptions in their activity can lead to complex metabolic consequences.