Purification and characterization of a novel protease from culture filtrates of a Streptomyces sp

Abstract A fibrinolytic protease has been isolated from Streptomyces sp. culture filtrate by successive chromatography on Mono S and Sephadex G50. The purified protease had a molecular mass of 33 kDa and had an isoelectric point of 6.7. It showed a sharp pH optimum at 7.8 with maximal protease activity between 35 °C and 50 °C. Its amino acid composition and aminoterminal sequence (17 residues) were determined. The protein exibited marked hydrolytic activity toward the substrates N-Succ-(Ala)2-Pro-Phe-pNA (Km= 0.77 mM, Vmax= 24.2 µmol mg−1 min−1) and N-Succ-(Ala)2-Pro-Leu-pNA (Km= 0.92 mM, Vmax= 7.7 µmol mg−1 min−1). It was totally inhibited by α1-antitrypsin, d-Phe-Pro-Arg-chloromethylketone and sodium dodecyl sulfate but was insensitive to EDTA, dithiothreitol, phenylmethylsulfonyl fluoride, soybean trypsin inhibitor, pepstatin or elastatinal. In this respect, this protease differed in its physico-chemical and biochemical properties from other extracellular proteases previously found in bacteria and fungi. The results suggest that it has properties of chymotrypsin-like serine-type proteases.