2Unit of Hemostasis, Central Clinical Laboratory, Military Medical Academy, G. Sofiiski Str. 3, 1603 Sofia, Bulgaria; fax: +359-2-952-6536; E-mail: firstname.lastname@example.org
3Laboratory of Enzymology, Department of Biochemistry, Faculty of Biology, Sofia University, Dr. Tsankov Ave. 8, 1164 Sofia, Bulgaria; fax: +359-2-865-6641; E-mail: email@example.com
* To whom correspondence should be addressed.
Received June 2, 2008; Revision received September 5, 2008
In the present study, we demonstrate for the first time that the potent neurotoxin vipoxin from the venom of Vipera ammodytes meridionalis exhibits hemolytic and anticoagulant properties. By investigating the effects of phospholipids and calcium ions on hemolysis, we established that the phospholipase A2 (PLA2) enzyme activity is responsible for the hemolytic properties. This was confirmed by chemical modification of the PLA2 active-site histidine residue with p-bromophenacylbromide. Applying different clotting assays, we show that the PLA2 is a weakly anticoagulant enzyme, which affects intrinsic tenase complex by the hydrolysis of procoagulant phospholipids, rather than by nonenzymatic mechanisms (binding to specific coagulation factors). The whole complex—vipoxin—does not affect the coagulation system.
KEY WORDS: vipoxin, phospholipase A2, hemolysis, anticoagulant activity