A comparison of aminoacyl-β-naphthylamide hydrolases in extracts of human tissues

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Abstract
The aminoacyl-[beta]-naphthylamide-hydrolase activities of extracts of human liver, kidney, pancreas and small intestine were partially purified by chromatography on DEAE [diethyl-aminoethyl]-Sephadex. The enzymes from the different tissues showed slight variations in chromatographic behavior and in mobility on starch-gel electrophoresis. Michaelis constants for the hydrolysis of L-leucyl- and L-alanyl-[beta]-naphthylamide by the partially purified enzyme fractions were determined by a spectrofluorimetric assay method. The enzymes from different sources gave similar Km values. L-Leucinamide and L-leucylglycine were competitive inhibitors of the hydrolysis of both substrates. Values of Ki (leucinamide) and Ki (leu-cylglycine) respectively were constant whatever combination of enzyme and substrate was used. The relevance of these results to the identity or non-identity of the enzymes from different tissues is discussed.