title: The effects of metal ions in Euphorbia cf. lactea latex on the fibrinogenolytic activity of a plant protease.
abstract: Two synchrotron-based techniques, synchrotron X-ray fluorescence (SXRF) and X-ray absorption spectroscopy (XAS), have demonstrated that Ca(2+) and Zn(2+) were the major metal ions distributed in the natural latex of Euphorbia cf. lactea. Both metal ions were found to affect the fibrinogenolytic activity of a homodimeric protease purified from the latex of this plant. The dimeric protein had an estimated molecular mass of about 82 kDa analyzed by SDS-PAGE. Therefore this protein was called as EuP-82. Based on the results of circular dichroism (CD) spectroscopy and the fibrinolytic activity measurement, it was found that Ca(2+) could activate the proteolytic activity of the enzyme by stabilizing its backbone structure. The intact conformation of EuP-82 was predicted from CD spectrum, which consisted of 51 % α-helix and 9 % β-sheet. Zn(2+) (10 mM) could decrease the fibrinolytic activity of EuP-82 to 30 ± 1 %. CD spectrum also supported that the inhibitory effect of Zn(2+) on the enzyme activity occurred by the drastic change of the enzyme structure with increasing the random coil conformation and by switching between α-helix and β-sheet structure. These results could be of first importance for further application to use EuP-82, the natural source protease as a potential drug for the thrombosis treatment. The fibrinolytic activity of EuP-82 may be enhanced by plasma Ca(2+) which generally involves in human hemostasis system.
authors.affiliation: School of Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand, jaruwan_siritape@yahoo.com.
authors.forename: Jaruwan
authors.initials: J
authors.lastname: Siritapetawee
authors.forename: Wanwisa
authors.initials: W
authors.lastname: Limphirat
authors.forename: Chortip
authors.initials: C
authors.lastname: Kantachot
authors.forename: Chanapa
authors.initials: C
authors.lastname: Kongmark
mesh_terms: D002118:Calcium / Q000097:blood / Q000737:chemistry*; D028481:Euphorbia / Q000737:chemistry / Q000201:enzymology*; D005342:Fibrinolysis / Q000187:drug effects; D005343:Fibrinolytic Agents / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007840:Latex / Q000737:chemistry; D010447:Peptide Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013052:Spectrometry, X-Ray Emission; D017356:Synchrotrons; D056928:X-Ray Absorption Spectroscopy; D015032:Zinc / Q000097:blood / Q000737:chemistry*
chemical_list: D005343:Fibrinolytic Agents; D007840:Latex; D010447:Peptide Hydrolases; D015032:Zinc; D002118:Calcium