Insight into S-adenosylmethionine biosynthesis from the crystal structures of the human methionine adenosyltransferase catalytic and regulatory subunits

MAT (methionine adenosyltransferase) utilizes L-methionine and ATP to form SAM (S-adenosylmethionine), the principal methyl donor in biological methylation. Mammals encode a liver-specific isoenzyme, MAT1A, that is genetically linked with an inborn metabolic disorder of hypermethioninaemia, as well as a ubiquitously expressed isoenzyme, MAT2A, whose enzymatic activity is regulated by an associated subunit MAT2B. To understand the molecular...