Methionine adenosyltransferase (EC 2.5.1.6) catalyzes the biosynthesis of S-adenosylmethionine (AdoMet) from methionine and ATP. AdoMet is the major methyl donor for many of the transmethylation reactions in the body.Three forms of MAT have been identified in mammalian tissues. MAT I and MAT III, which are encoded by the single-copy MAT1A gene, represent tetramers and dimers, respectively, formed from identical alpha-1 subunits and are synthesized primarily in the liver. The MAT2A promoter is highly GC rich, especially in the first 300 bp. The promoter contains several potential SP1-, v-myb-, and GATA-binding sites, as well as potential binding sites for C/EBP, HSF2, c-myb, and STATx.MAT2A promoter can efficiently drive expression from a reporter gene in both Jurkat and 293 cells.