Earthworms active components from

Zhou et al. [5] found that at least seven components with fibrinolytic activity from earthworm E. fetida, Fig. (1). Three components are purified by fast protein liquid chromatography and proved to be homogenous on sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), with apparent molecular masses 30,000, 25,000 and 30,000 Da, respectively. These enzymes are stable at pH 5 9, but totally denaturated below pH 2.6. 

In the recent studies, the enzyme shows that the overall polypeptide fold of chymotrypsin-like serine protease possesses essential SI specificity determinants characteristic of elastase using the multiple isomorphous replacement (MIR) method and refined to 2.3 A resolution Fig. (5). Structure-based inhibitor modeling demonstrated that EFEa s SI specificity pocket is preferable for elastase-specific small hydrophobic PI residues, while its accommodation of long and/or bulky PI residues is also feasible if enhanced binding of the substrate and induced fit of the SI pocket are achieved [Fig. (6) shows the active sites of serine protease]. EFEa is thereby endowed with relatively broad substrate specificity, including the dual fibrinolysis. This structure is the first report of an earthworm fibrinolytic enzyme component, a serine protease originated from annelid worm [17]. 

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