Purification and characterization of a novel fibrinolytic enzyme from the polychaete, Neanthes japonica (Iznka)

A novel fibrinolytic enzyme from Neanthes japonica (Iznka), named NJF, was purified to electrophoretic homogeneity using ammonium sulfate precipitation, hydrophobic interaction, ion exchange and gel-filtration chromatography. NJF consisted of a single polypeptide chain with a molecular weight of 28–32 kDa, which was determined by MALDI-TOF mass spectrum and SDS–PAGE. The isoelectric point of NJF determined by isoelectric focusing electrophoresis (IEF) was 4.4, and the maximum activity of the enzyme was observed at 60 °C and pH 9.0. The cleavage speed of fibrinogen by NJF affected the Aα-chain first, followed by the Bβ-chain and finally the γ-chain. NJF activity was strongly inhibited by PMSF, indicating that it is a serine protease. Partial amino-acid sequences of its fragments were different from those of other known fibrinolytic enzymes. N. japonica may thus represent a potential source of new therapeutic agents to treat thrombosis.