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