N-terminal processing: the methionine aminopeptidase and N alpha-acetyl transferase families.

Removal of the initiator methionine and/or acetylation of the alpha-amino group are among the earliest possible chemical modifications that occur during protein synthesis in eukaryotes. These events are catalyzed by methionine aminopeptidase and N alpha-acetyltransferase, respectively. Recent advances in the isolation and characterization of these enzymes indicate that they exist as isoforms that vary in cellular location, function, and evolutionary origins.