Blood, 1966, Vol. 27, No. 4, pp. 527-536.
© 1966 American Society of Hematology, Inc.
The Activation of Proaccelerin by Bovine Thrombokinase
(with Notes on the Antithrombic Activity of
Phenylmethyl Sulfonylfluoride)
ROBERT T. BRECKENRIDGE 1 and
OSCAR D. RATNOFF 1
1 Department of Medicine, Western Reserve University School of Medicine and University Hospitals of Cleveland, Cleveland, Ohio.
Through the kindness of Dr. J. H. Milstone we were able to perform clotting
studies with purified bovine thrombokinase. Phenylmethyl sulfonylfluoride was
found to inactivate bovine thrombin. Bovine thrombokinase, freed of traces of
contaminating thrombin by treatment with phenylmethyl sulfonylfluoride, behaved in a manner similar to activated Stuart factor. Kinetic studies with this
purified clotting factor and partially purified bovine proaccelerin supported the
hypothesis that bovine proaccelerin is changed by the enzymatic action of
thrombokinase to an agent which converts prothrombin to thrombin. The
reaction between thrombokinase and bovine proaccelerin requires phospholipid and calcium and is blocked by soybean trypsin inhibitor. The similarities
between human activated Stuart factor and bovine thrombokinase are apparent.
Submitted on May 10, 1965
Accepted on August 2, 1965
