MTHFR (Methylenetetrahydrofolate Reductase): MTHFR is an enzyme that plays a central role in folate metabolism and the regulation of homocysteine levels. It converts 5,10-methylenetetrahydrofolate into 5-methyltetrahydrofolate, enabling the remethylation of homocysteine to methionine — a precursor to S-adenosylmethionine (SAM), the body’s primary methyl donor. Variants in the MTHFR gene, such as C677T and A1298C, can affect enzyme activity, potentially altering folate metabolism, raising homocysteine levels, and impacting methylation-dependent processes like DNA methylation and neurotransmitter synthesis.