The substrate specificity of an aminopeptidase (neutral arylamidase) from pig brain

Neutral arylamidase of pig brain has been purified 235 fold. At this purification the major band on disc-gel electrophoresis is associated with the enzyme activity, although several minor components are also present. The arylamidase is -SH dependent and puromycin inhibited. It has activity toward lysyl and arginyl beta-naphthylamides as well as toward the beta-naphthylamides of a large variety of neutral amino acids. The enzyme is strongly substrate inhibited, making the relative order of reactivity to aminoacyl beta-naphthylamides dependent upon the substrate concentration chosen for comparison. It also shows activity toward certain di-, tri-, and oligopeptides. When more than one residue is cleaved, the release is sequential, starting from the amino terminus of the peptide. It appears therefore that pig brain neutral arylamidase is an aminooligopeptidase of broad specificity. We suggest that beta-naphthylamides are model substrates representing the N-terminal end of peptides with three or more residues. The properties of pig brain enzyme are similar in many respects to those previously isolated from rat and bovine brain and bovine pituitary.