Purification and characterization of a novel metalloproteinase, acurhagin, from Agkistrodon acutus venom.

Acurhagin, a high-molecular mass hemorrhagic metalloproteinase, was purified from the crude venom of Agkistrodon acutus using anion-exchange and hydrophobic interaction chromatography. Acurhagin is a monomer with a molecular mass of 51.4 kDa under non-reducing conditions on SDS-PAGE and 48,133 Da by mass spectrometry. Partial amino acid sequence of its metalloproteinase domain is homologous to other high-molecular mass metalloproteinases from snake venoms. It preferentially cleaved Aalpa chain of fibrinogen, followed by Bbeta chain, while gamma chains was minimally affected. Monitored by RP-HPLC, it extensively degraded fibrinogen into various peptide fragments. In aqueous solution, acurhagin autoproteolyzed to a 30 kDa fragment at 37 degrees C. The N-terminal sequence of the 30 kDa fragment of acurhagin showed a high homology to those proteins consisting of disintegrin-like and cysteine-rich domains. Caseinolytic assay showed that the proteinase activity of acurhagin was slightly enhanced by Ca2+ and Mg2+, but completely inhibited by Zn2+. When treated with metal chelators, acurhagin was completely inactivated. Furthermore, acurhagin exerts an inhibitory effect on ADP-induced platelet aggregation of platelet-rich plasma in an incubation-time dependent manner. It also impairs collagen- and ristocetin-induced platelet aggregation by cleaving collagen and vWF, respectively.