MAT (Methionine adenosyltransferase) is an important enzyme involved in the metabolism of methionine, converting methionine into S-adenosylmethionine (SAM). The main family members include MAT1A, MAT2A, and MAT2B, which consist of multiple functional domains and are mainly located in the cytoplasm and mitochondria of the liver and other tissues. MAT is involved in regulating one-carbon metabolism, methylation reactions, and various biological processes such as gene expression regulation, cell proliferation, and apoptosis. The expression of MAT family members is tissue- and cell-specific, and mutations or dysregulation of their genes are associated with various diseases, including liver diseases, cancer, and neurological disorders.