Differential Proteolytic Activation of Factor VIII--von Willebrand Factor Complex by Thrombin

• Published in: Proceedings of the National Academy of Sciences - PNAS 1989-09, Vol.86 (17), p.6508-6512
• Main Authors: Hill-Eubanks, David C., Parker, Carlo G., Lollar, Pete
• Format: Article
• Language: English
• Subjects: 550201 - Biochemistry- Tracer Techniques; Amino acids; ANIMALS; BASIC BIOLOGICAL SCIENCES; Benzamidines; BETA DECAY RADIOISOTOPES; BIOCHEMISTRY; Biological and medical sciences; BIOLOGICAL MATERIALS; BLOOD; BLOOD COAGULATION FACTORS; Blood coagulation. Blood cells; BLOOD PLASMA; BODY FLUIDS; Bothrops jararacussu; CHEMICAL ACTIVATION; CHEMICAL REACTIONS; CHEMISTRY; CHROMATOGRAPHY; COAGULANTS; Coagulation factors; DAYS LIVING RADIOISOTOPES; DECOMPOSITION; DISEASES; DRUGS; ELECTRON CAPTURE RADIOISOTOPES; ELECTROPHORESIS; ENZYMATIC HYDROLYSIS; Enzyme Activation; ENZYMES; Factor VIII - metabolism; Fundamental and applied biological sciences. Psychology; HEMATOLOGIC AGENTS; HEMIC DISEASES; HEMOPHILIA; HEMOSTATICS; HEREDITARY DISEASES; Humans; HYDROLASES; HYDROLYSIS; INTERMEDIATE MASS NUCLEI; IODINE 125; IODINE ISOTOPES; ION EXCHANGE CHROMATOGRAPHY; ISOTOPES; Kinetics; LYSIS; Macromolecular Substances; MAMMALS; MAN; MATERIALS; Molecular and cellular biology; MOLECULAR STRUCTURE; NUCLEI; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; PEPTIDE HYDROLASES; Platelet Aggregation; Platelets; PRIMATES; PROTEINS; RADIOISOTOPES; SEPARATION PROCESSES; Sequence analysis; serine proteinase; SERINE PROTEINASES; Snake venoms; Snake Venoms - isolation & purification; SOLVOLYSIS; Swine; THROMBIN; Thrombin - metabolism; venom; VENOMS; VERTEBRATES; von Willebrand factor; von Willebrand Factor - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.86.17.6508

Blood coagulation factor VIII (fVIII) is a plasma protein that is decreased or absent in hemophilia A. It is isolated as a mixture of heterodimers that contain a variably sized heavy chain and a common light chain. Thrombin catalyzes the activation of fVIII in a reaction that is associated with cleavages in both types of chain. We isolated a serine protease from Bothrops jararacussu snake venom that catalyzes thrombin-like heavy-chain cleavage but not light-chain cleavage in porcine fVIII as judged by NaDodSO4/PAGE and N-terminal sequence analysis. Using a plasma-free assay of the ability of activated fVIII to function as a cofactor in the activation of factor X by factor IXa, we found that fVIII is activated by the venom enzyme. The venom enzyme-activated fVIII was isolated in stable form by cation-exchange HPLC. von Willebrand factor inhibited venom enzyme-activated fVIII but not thrombin-activated fVIII. These results suggest that the binding of fVIII to von Willebrand factor depends on the presence of an intact light chain and that activated fVIII must dissociate from von Willebrand factor to exert its cofactor effect. Thus, proteolytic activation of fVIII--von Willebrand factor complex appears to be differentially regulated by light-chain cleavage to dissociate the complex and heavy-chain cleavage to activate the cofactor function.