Biomaterial Database

The kinetic assembly of the intrinsic bovine factor X activation system. 1989

J M Beals, and B A Chibber, and F J Castellino

Department of Chemistry, University of Notre Dame, Indiana 46556.

The activation of bovine factor X by bovine factors IXa alpha and IXa beta has been examined under conditions of progressive assembly of the complete intrinsic activation system, i.e., factor X/factor IXa/Ca2+/phospholipid (PL)/factor VIIIa. In the presence of Ca2+, and the absence of PL and factor VIIIa, factor IXa alpha is a more efficient enzyme than factor IXa beta toward factor X activation, primarily due to the much higher kcat for the factor IXa alpha-catalyzed reaction. Analysis of the steady-state kinetic properties, after addition of PL (mixtures of phosphatidylcholine/phosphatidylserine) to the factor X/factor IXa/Ca2+ activation system, shows that the mechanism most closely follows a nonessential activation scheme, where the true substrate is the factor X/Ca2+/PL complex. The presence of PL results in a large (1-2 orders of magnitude) increase of the kcat for factor IXa beta, but does not substantially affect the steady-state kinetic constants of the factor IXa alpha-catalyzed reaction. Examination of the steady-state activation kinetics of factor X, after addition of factor VIIIa to factor X/factor IXa/Ca2+/PL, demonstrates that the mechanism is most consistent with a nonessential activation scheme of fluid phase substrate (factor X) being activated by a PL-bound enzyme system (factor IXa/Ca2+/factor VIIIa/PL). The presence of factor VIIIa stimulated the rates of factor X activation by factor IXa beta/Ca2+/PL by 1-2 orders of magnitude. Qualitatively similar behavior was noted for the factor IXa alpha-catalyzed activation. The results of this manuscript show that, in the presence of Ca2+ and absence of other cofactors, factor IXa alpha is a much more efficient enzyme for factor X activation, as compared to factor IXa beta. This is likely due to effects on the system resulting from covalent retention of the negatively charged activation peptide, by factor IXa alpha. However, the enzymatic activity of factor IXa beta shows a far better response to cofactors, particularly PL, than factor IXa alpha, thereby rendering factor IXa beta the more efficient enzyme in the complete intrinsic activation system.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D010743	Phospholipids	Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system.	Phosphatides,Phospholipid
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D004789	Enzyme Activation	Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.	Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D005164	Factor IX	Storage-stable blood coagulation factor acting in the intrinsic pathway of blood coagulation. Its activated form, IXa, forms a complex with factor VIII and calcium on platelet factor 3 to activate factor X to Xa. Deficiency of factor IX results in HEMOPHILIA B (Christmas Disease).	Autoprothrombin II,Christmas Factor,Coagulation Factor IX,Plasma Thromboplastin Component,Blood Coagulation Factor IX,Factor 9,Factor IX Complex,Factor IX Fraction,Factor Nine,Factor IX, Coagulation
D005169	Factor VIII	Factor VIII of blood coagulation. Antihemophilic factor that is part of the factor VIII/von Willebrand factor complex. Factor VIII is produced in the liver and acts in the intrinsic pathway of blood coagulation. It serves as a cofactor in factor X activation and this action is markedly enhanced by small amounts of thrombin.	Coagulation Factor VIII,Factor VIII Clotting Antigen,Factor VIII Coagulant Antigen,Factor VIII Procoagulant Activity,Thromboplastinogen,Blood Coagulation Factor VIII,F VIII-C,Factor 8,Factor 8 C,Factor Eight,Factor VIIIC,Hyate-C,Hyatt-C,F VIII C,Hyate C,HyateC,Hyatt C,HyattC
D005170	Factor X	Storage-stable glycoprotein blood coagulation factor that can be activated to factor Xa by both the intrinsic and extrinsic pathways. A deficiency of factor X, sometimes called Stuart-Prower factor deficiency, may lead to a systemic coagulation disorder.	Autoprothrombin III,Coagulation Factor X,Stuart Factor,Stuart-Prower Factor,Blood Coagulation Factor X,Factor 10,Factor Ten,Stuart Prower Factor,Factor X, Coagulation
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular