S-ADENOSYLMETHIONINE SYNTHESIS - MOLECULAR MECHANISMS AND CLINICAL IMPLICATIONS

Methionine adenosyltransferase (MAT) is an ubiquitous enzyme that cata lyzes the synthesis of S-adenosylmethionine from methionine and ATP. I n mammals, there are two genes coding far MAT, one expressed exclusive ly in the liver and a second enzyme present in all tissues. Molecular studies indicate that liver MAT exists in two forms: as a homodimer an d as a homotetramer of the same oligomeric subunit. The liver-specific isoenzymes are inhibited in human liver cirrhosis, and this is the ca use of the abnormal metabolism of methionine in these subjects. (C) 19 97 Elsevier Science Inc.