Fibrinolytic activity of a novel serine protease from the hemolymph of a polychaeta, Periserrula leucophryna

We purified and characterized a novel protease with fibrinolytic activity from the hemolymph of a polychaeta, Periserrula leucophryna. The enzyme was isolated by chromatographic methods using Phenyl-Sepharose and Benzamidine-Sepharose. SDS-PAGE and gel filtration revealed a single polypeptide chain with a molecular weight of 30 kDa. The N-terminal sequence was determined to be IVGGQNARQGEFPWQV. The purified enzyme preferentially cleaved the synthetic substrates that had Lys (rather than Arg) at the P₁ position and did not efficiently cleave substrates with non-polar amino acids. Among chromogenic protease substrates, the substrate that was most susceptible to hydrolysis by Periserrula leucophryna fibrinolytic protease (PLFP) was Val-Leu-Lys-pNA (substrate for plasmin). The inhibition profile revealed the protease belongs to a family of serine proteases and has plasmin-like activity that is strongly inhibited by α2-antiplasmin. The purified PLFP was able to dissolve the artificial fibrin, and its fibrinolytic behavior is similar to that of plasmin. In conclusion, PLFP is a novel protease and has potential for practical applications in thrombolytic therapy.