Methionyl aminopeptidase from rat liver: distribution of the membrane-bound subcellular enzyme.

The selective distribution of methionyl aminopeptidase (MAP) among rat liver mitochondria (heavy and light) and microsomes is reported. Several properties of MAP from the three subcellular fractions showed that the enzyme is a typical aminopeptidase able to remove N-terminal methionine from oligopeptides and methionyl-2-naphthylamide but not from Met-Ala-Ser. MAP is a membrane-bound enzyme sensitive to SH-group oxidants and inhibitable by L-methionine but not by usual arylaminopeptidase inhibitors. It is suggested that, MAP may play an important role during protein synthesis in rat liver.