A fibrinolytic protease (FP84) was purified from Streptomyces sp. CS684, with the aim of isolating economically viable enzyme from a microbial source. SDS-PAGE and fibrin zymography of the purified enzyme showed a single protein band of approximately 35 kDa. Maximal activity was at 45 degrees C and pH 78, and the enzyme was stable between pH 6 and 9 and below 40 degrees C. It exhibited fibrinolytic activity, which is stronger than that of plasmin. FP84 hydrolyzed B beta-chains of fibrinogen, but did not cleave A alpha- and gamma-chains. K(m), V(max) and K(cat) values for azocasein were 4.2 mg ml(-1). 305.8 mu g min(-1) mg(-1) and 188.7 s(-1), respectively. The activity was suppressed by Co(2+), Zn(2+), Cu(2+) and Fe(2+), but slightly enhanced by Ca(2+) and Mg(+2). Additionally, the activity was slightly inhibited by aprotinin and PMSF, but significantly inhibited by pefabloc, EDTA and ECTA. The first 15 amino acids of N-terminal sequence were GTQENPPSSGLDDID. They are highly similar to those of serine proteases from various Streptomyces strains, but different with known fibrinolytic enzymes. These results suggest that FP84 is a novel serine metalloprotease with potential application in thrombolytic therapy. (C) 2009 Elsevier Ltd. All rights reserved.