Purification and characterization of a novel protease from culture filtrates of a<i>Streptomyces</i>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 degrees C and 50 degrees C. Its amino acid composition and amino-terminal sequence (17 residues) were determined. The protein exhibited marked hydrolytic activity toward the substrates N-Succ-(Ala)2-Pro-Phe-pNA (K(m) = 0.77 mM, Vmax = 24.2 mumol mg-1 min-1) and N-Succ-(Ala)2-Pro-Leu-pNA (K(m) = 0.92 mM, Vmax = 7.7 mumol mg-1 min-1). It was totally inhibited by alpha 1-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.