MAT1A (methionine adenosyltransferase 1A) catalyzes the biosynthesis of S-adenosylmethionine (SAM), the principal biological methyl donor in cells, from methionine and ATP 1. This enzyme is predominantly expressed in normal liver tissue, where it generates the majority of cellular SAM 1. MAT1A functions as a metabolic sensor; during fasting, glucagon induces MAT1A expression, causing it to translocate to mitochondria-associated membranes where SAM production modulates fatty acid oxidation and ATP synthesis 2. The enzyme is sensitive to environmental and endogenous stressors—formaldehyde exposure inhibits MAT1A activity by reacting with critical cysteine residues, reducing SAM production and epigenetic modifications 3. Clinically, MAT1A dysfunction has significant disease implications. Reduced MAT1A expression and SAM levels occur in hepatocellular carcinoma (HCC), contributing to DNA hypomethylation, genomic instability, and activation of oncogenic signaling pathways 4. The MAT1A:MAT2A expression ratio inversely correlates with cell proliferation and genomic instability while predicting patient survival 4. In non-small cell lung cancer, MAT1A promotes glycolysis and cell proliferation by stabilizing cyclin D1 5. Conversely, hepatic MAT1A and its binding partner PHB1 defend against cancer metastasis by suppressing matrix metalloproteinase-7 6. MAT1A deficiency is associated with oxidative stress and steatohepatitis 1, highlighting the critical importance of maintaining physiological SAM levels for liver health.