A novel fibrinolytic serine metalloprotease from the marine Serratia marcescens subsp. sakuensis: Purification and characterization

This study demonstrates the purification and characterization of a fibrinolytic serine metalloprotease from the marine Serratia marcescens subsp. sakuensis (KU296189.1). The purified enzyme (1033 U/mg) had a molecular weight of 43 KDa, with optimum pH and temperature being 7 and 55 °C. The in vitro half-life of the fibrinolytic enzyme at 37 °C was found to be 19 h. The kinetic constants, Km and Vmax of the purified enzyme determined using fibrin as substrate was 0.66 mg/mL and 158.73 U/mL. The Kcat and catalytic efficiency of the enzyme was found to be 12.21 min-1 and 18.32 mL/(mg min) respectively. The fibrinolytic enzyme did not show any proteolytic activity towards blood plasma proteins like haemoglobin, γ-globulins and transferrin. In vitro studies revealed that the fibrinolytic enzyme displayed 38% clot lysis for a period of 3 h which was higher than that displayed by streptokinase and heparin. A total of seven peptide sequences were obtained after the LC-MS/MS-TOF analysis, out of which only four sequences showed 67% homology with the sequences of the other proteases. All these results suggest its novelty and potential application in thrombolytic therapy.