Purification and physicochemical characterization of a serine protease with fibrinolytic activity from latex of a medicinal herb Euphorbia hirta

A 34 kDa serine protease, designated as hirtin, with fibrinolytic activity was purified to homogeneity from the latex of Euphorbia hirta by the combination of ion exchange and gel filtration chromatography. The N-terminal sequence of hirtin was found to be YAVYIGLILETAA/NNE. Hirtin exhibited esterase and amidase activities along with azocaseinolytic, gelatinolytic, fibrinogenolytic and fibrinolytic activities. It preferentially hydrolyzed Aα and α-chains, followed by Bβ and β, and γ and γ–γ chains of fibrinogen and fibrin clot respectively. The optimum pH and temperature for enzyme activity was found to be pH 7.2 and 50 °C respectively. Enzymatic activity of hirtin was significantly inhibited by PMSF and AEBSF. It showed higher specificity for synthetic substrate p-tos-GPRNA for thrombin. The CD spectra of hirtin showed a high content of β-sheets as compared to α-helix. The results indicate that hirtin is a thrombin-like serine protease and may have potential industrial and therapeutic applications.

A 34 kDa thrombin-like serine protease with fibrinolytic activity was characterized from the latex of the Euphorbia hirta belonging to the Euphorbiaceae family.Figure optionsDownload as PowerPoint slideHighlights
► A 34 kDa thrombin-like serine protease characterized from latex of Euphorbia hirta.
► It is stable over a wide range of pH and temperature.
► The optimum pH and temperature was found to be pH 7.2 and 50 °C respectively.
► It possesses fibrinogenolytic as well as fibrinolytic activities.
► The enzyme may have potential therapeutic and industrial applications.