[Proteolysis of prothrombin by beta/gamma thrombin]

beta/gamma-thrombin containing 25% of beta-form and 75% of gamma-form was obtained from alpha-thrombin by limited trypsin proteolysis. As compared to the parent alpha-thrombin, these preparations preserved less than 0.02% of fibrinogen-clotting activity, the entire esterase activity and 27% of the amidolytic activity toward N-benzoyl-Phe-Val-Arg-p-nitroanilide. Like alpha-thrombin, beta/gamma-thrombin splits prothrombin to prethrombin I (Mr 58000) and fragment I of prothrombin (Mr 25000) possessing antithrombin activity. Kinetics of prothrombin hydrolysis was studied by different concentrations of enzymes. It was shown that alpha-form is more specific than beta/gamma-form that preserved approximately 5% of prothrombinolytic activity of alpha-thrombin. It is emphasized that beta/gamma-form devoid of clotting activity retains regulatory functions.