A comparison of aminoacyl-beta-naphthylamide hydrolases in extracts of human tissues.

1. The aminoacyl-beta-naphthylamide-hydrolase activities of extracts of human liver, kidney, pancreas and small intestine were partially purified by chromatography on DEAE-Sephadex. 2. The enzymes from the different tissues showed slight variations in chromatographic behaviour and in mobility on starch-gel electrophoresis. 3. 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 K(m) values. 4. l-Leucinamide and l-leucylglycine were competitive inhibitors of the hydrolysis of both substrates. Values of K(i) (leucinamide) and K(i) (leucylglycine) respectively were constant whatever combination of enzyme and substrate was used. 5. The relevance of these results to the identity or non-identity of the enzymes from different tissues is discussed.