text: Different substrates were used as the relative specific substrates for the determination of aminopeptidase enzymatic activity: 4-methoxy-2-naphthylamide of L-alanine for aminopeptidase N, 4-methoxy-2-naphthylamide of L-leucine for leucine aminopeptidase, << 4-methoxy-2-naphthylamide >> of L-glutamic acid for [[ aminopeptidase A ]] and 4-methoxy-2-naphthylamide of L-arginine for aminopeptidase B.