In order to understand the function of activated factor V in the prothrombinase complex, we isolated the activation products obtained by action of thrombin and RVV-V on factor V and studied their functional properties. Factor V isolated from plasma by means of ion-exchange chromatography, a Ca-oxalate adsorption step and gelfiltration was homogenous in SDS-gelelectrophoresis (apparent MW 360,000, with and without reduction). Increase in factor V activity upon action by RVV-V is correlated with a single peptide bond cleavage, resulting in a 270,000 dalton and a 80,000 dalton component. Additional proteolysis of factor Va(RVV/V)’ by thrombin results in a further cleavage of the high MW component into peptides with MW's of 72,000, 94,000 and about 150,000 without a furth~r increase in factor V activity. Whereas none of the isolated peptides reveal factor Va activity, activity would be generated by a recombination in the presence of Ca2+ of the 94,000 MW or 270,000 MW component with the 80,000 component. Action of thrombin alone on factor V results in peptides of MW 72,000, 80,000, 94,000 and a peptide very rich in carbohydrate with an apparent MW of 150,000.
Comparative study of protease hydrolysis reaction demonstrating Normalized Peptide Bond Cleavage Frequency and Protease Substrate Broadness Index
