[Modification effect of the protein component of tissue thromboplastin (factor III) on its interaction with factors VII and X].

The role of protein moiety of tissue thromboplastin during its specific enzymatic modification by papain was studied. Treatment with papain was followed by a decrease of the number of binding sites for factor X on the surface of factor III. The ability of the remaining sites to bind factor X and to form prothrombinase complexes did not change thereby. The specific interaction of thromboplastin with the factors coupled with the external blood coagulation system are based on asymmetric distribution of phospholipids and apoprotein in the cell membrane.