[A membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus. 2. Substrate specificity of the enzyme]

The substrate specificity of the membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus was investigated with a series of substituted amides of alpha-amino acids. In contrast to mammalian AAP forms, the rate of hydrolysis of the AAP from Acinetobacter calcoaceticus is higher using 4-nitranilide than 2-naphthylamide substrates. The enzyme affinity is very high for alanine substrates and decreases in the series of the amide substituents, from methyl coumarylamides, 4-nitranilides, 4-methoxynaphthylamides to the 2-naphthylamides. The alanine aminopeptidase shows its highest affinity to Ala-MCA (Km = 77 mumol(s)/1).