Seven chromogenic substrates were used to establish the identity of the classical leucine aminopeptidase. These substrates were the leucyl, glycyl, alanyl, phenylalanyl, methionyl, glutamyl, and arginyl amides of 2-naphthylamine. The cleavage of these substrates was studied by the enzyme (or enzymes) in four organs of the rat, and in the livers of five species. The rate constants, pH optima, influence of temperature, aging and fixation effects, and activities with substrate combinations were determined. Substrate hydrolysis by a purified preparation of leucine aminopeptidase was measured also. The currently available information would seem to favor the nonspecificity of aminopeptidase, with the likelihood that more than one aminopeptidase exists. Even though certain peptides may be preferentially hydrolyzed, there is so much overlap that the characterization of the specific aminopeptidase by its amino acid preference serves no more useful function than to label the substrate used. Therefore it is unrealistic to characterize the enzyme by the amino acid used, if a more specific implication is intended.
ASJC Scopus subject areas
- Molecular Biology