Anti-Sam-S antibodies are protein reagents that detect specific antigens. The Sam-S antigen is another term for the human protein methionine adenosyltransferase 1A, encoded by the MAT1A gene. The protein is known to catalyze the formation of S-adenosylmethionine from methionine and ATP. Canonically, it has an amino acid length of 395 residues and a mass of 43.6 kilodaltons. and it is notably expressed in the liver. The Sam-S protein is a member of the AdoMet synthase protein family.