THE SEPARATION OF AUTOPROTHROMBIN IcFROM BOVINE PROTHROMBIN PREPARATIONS

Abstract

Autoprothrombin Ic is a degradation product of purified prothrombin which is obtained when the enzyme autoprothrombin C is used for activation. A quantitative method was developed for the assay of autoprothrombin Ic. Conditions were found for activating purified prothrombin so as to obtain the maximum yield of autoprothrombin Ic. Isolation procedures were developed for obtaining a single component. The specific activity was in the range 32,000 to 34,000 units/mg tyrosine or 1440 U./mg. The yield was about 4 mg from 6 liters of plasma. By contrast with autoprothrombin C it did not by itself alter prothrombin activity. In the presence of lipids, calcium ions, and Ac-globulin it was found to be a powerful procoagulant. Plasma and serum contain a substance that destroys the activity. The activity was also destroyed by reduced glutathione, iodoacetate, and ascorbic acid, but it was relatively resistant to SH blocking agents. In the prothrombin utilization test purified autoprothrombin Ic gave prothrombin consumption with Stuart plasma and with factor VII deficient plasma. With 0.5 [mu]g in the test mixture (0.3 ml) the prothrombin time of Stuart plasma was completely corrected. With 60 [mu]g the clotting time was 8 seconds.