MAT1A (Methionine Adenosyltransferase I, Alpha) is an enzyme that produces S-adenosylmethionine (SAMe), the body’s primary methyl donor for key metabolic processes. It plays a central role in methionine metabolism, influencing gene regulation, cell growth, and detoxification. Reduced MAT1A activity is linked to liver disorders such as cirrhosis and hepatocellular carcinoma.