ISSN:
1573-4943
Keywords:
blood coagulation factor V
;
snake venoms
;
thrombocytin
;
Russell's viper venom protease
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Thrombin activation of factor V constitutes an important feedback reaction in the regulation of coagulation. We therefore examined the details of activation of bovine factor V by two purified snake venom proteolytic enzymes, factor V-activating protease from Russell's viper venom and a platelet-aggregating enzyme, thrombocytin, fromBothrops atrox venom. The reactions were followed by changes in factor V coagulant activity, immunoelectrophoresis, and electrophoresis of radiolabeled factor V in sodium dodecylsulfate under reducing conditions. When factor V (M r 330,000) was exposed to factor V-activating protease at an enzyme-to-substrate ratio of 1:35 at 37°, cleavage occurred in 1 min, with formation of an intermediate (M r 250,000) coincident with a nine-fold activity increase. By 2 min, additional cleavage occurred, with disappearance of the intermediate and formation of two final fragments (M r 150,000 and 100,000) but no further change in coagulant activity. The concentration of these components remained unchanged from 5 to 15 min. Immunoelectrophoresis against antiserum directed against factor V confirmed cleavage of the molecule. Incubation of factor V with thrombocytin at 37° for 1 min resulted in a four-fold increase of factor V activity, with the formation of an intermediate (M r 220,000). By 2 min, a 7.5-fold activation was found, with a decline in the concentration of the intermediate; the predominant species hasM r =130,000. At 5 min the intermediate disappeared and a second, final fragment ofM r of ∼150,000 appeared without further change in coagulant activity. Immunoelectrophoresis again confirmed selective proteolysis. Thus, incubation of factor V-activating protease or thrombocytin with factor V results in different molecular alterations associated with an increase in the coagulant activity of this clotting factor.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01025352
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