The ground beetle of E. sinensis has been used in East Asia as crude drugs for thrombolytic therapy and is presently reared as a medicinal insect in China. In order to identify and characterize the interesting thrombolytic compounds and help in identifying novel thrombolytic candidates, we investigate thrombolytic molecules in the insect of E. sinensis. A thrombolytic protein (Eupolytin1) was purified and characterized from mid-guts of the medicinal insect of E. sinensi. It is composed of 226 aa(GenBank accession Gu187070). BLAST search revealed that it is a novel protein belonging to serine protease family. Eupolytin1 could hydrolyze chromogenic substrates T6140 and B3133, indicating that eupolytin1 contains plasmin- and trypsin-like activities. Similar to plasmin, eupolytin1 contains ability to hydrolyze fibrinogen and fibrin. Eupolytin1 showed strong fibrino(gen)olytic activities; 20 mg fibrinogen could be completely hydrolyzed by 1 mg eupolytin1 during 1.5 h. Different from known fibrino(gen)olytic enzymes which only hydrolyze α- or/and β-chains of fibrinogen, eupolytin1 could hydrolyze α-, β-, and γ-chains of fibrinogen. In addition to directly hydrolyzing fibrin(ogen) (direct-acting) , Eupolytin1 could activate plasminogen to hydrolyze fibrin (indirect-acting). The synergetic action of these two means (direct- acting and indirect-acting) obviously improved the fibrinolysis efficiency of eupolytin 1. Such type of bi-functional agent containing both plasmin- and PA-like activities has more advantages than known anti-thrombosis agents to treat thrombus.
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