Identification Of Two Dysthrombins Derived From Prothrombin Quick

A dysfunctional thrombin, Thrombin Quick, derived from the congenital dysprothrombin, Prothrombin Quick, had 3040 percent of normal thrombin activity on the low molecular weight substrates, benzoyl arginine ethylester, tosyl-gly-pro-arg-p-nitroanilide, and carbobenzoxylysine-p-nitro-phenylesier, but only 2-5 percent of normal activity in Factor V and Factor VIII activation and platelet aggregation. Titration with the high affinity competitive inhibitor of thrombin, dansyl-arginine-N-(3-ethyl-l, 5-pentanediyl)amide (DAPA) indicated an active site concentration of 0.4 per mole protein. Further studies indicated that the Thrombin Quick preparation could be eluted from sulfopropyl Sephadex as two components, one of which did not show fluorescence enhancement on treatment with DAPA nor did it possess tripeptidase activity. Further analytical chromatography on sulfopropyl Sephadex indicated that the two Thrombin Quick components are chromatographically distinct from thrombin and that their elution pattern is not altered by treatment with thrombin. Each of the Thrombin Quick components was rechromatographed in the presence of thrombin. There was no indication of interconversion of the two components. The results indicate that the presence of two components in Thrombin Quick is not related to the incomplete cleavage of a 13 residue peptide from the amino terminus of the thrombin A chain which occurs in normal thrombin. A synthetic substrate assay was used to determine relative activities of 0.38, 0.45 and 0.33 for Prothrombin Quick, Prethrombin 1 Quick and Thrombin Quick, respectively, compared to their normal counterparts. The simplest explanation for the occurrence of the two Thrombin Quick species is that they are derived from two genetic allomers of prothrombin.