Purification and characterization of a soluble methionyl aminopeptidase from porcine skeletal muscle

A soluble aminopeptidase was purified from porcine skeletal muscle by ammonium sulfate fractionation and two successive anion exchange chromatographic procedures. The enzyme eluted at 0.17 M NaCl, had a relative molecular mass of 53 KDa (by SDS-polyacrylamide gel electrophoresis) and was activated by sulfydryl compounds. Activity was optimal at pH 7.5 and 40°C and showed broad aminopeptidase and low endopeptidase activities. The aminopeptidase exhibited maximal activity against Met-, Lys-, Ala-, and Leu-7-amido-4-methyl-coumarin (-AMC), while Pro-AMC was not hydrolyzed. Inhibition of enzyme activity was observed in the presence of sulfydryl reagents, iodoacetic acid, puromycin, leupeptin and amastatin, but it was not affected by serin and aspartic protease inhibitors, EDTA and bestatin. The enzyme activity was not inhibited by sodium chloride and, therefore, the enzyme has potential for contributing to the generation of free amino acids in cured pork meat products.