Effects of lipid-binding proteins apo A-I, apo A-IL, beta 2-glycoprotein I, and C-reactive protein on activation of factor X by tissue factor--factor VIIa.
Tissue factor is the membrane-associated protein which mediates activation of factors IX and X by factor VII. In a purified, reconstituted bovine system, factor X activation by the tissue factor-factor VIIa complex is inhibited by the mixed apoproteins from human high density lipoprotein (HDL) and by isolated apolipo-protein A-II (apo A-II). Other proteins found associated with plasma lipoproteins, apolipoprotein A-I (apo A-I), C-reactive protein (CRP), and beta 2-glycoprotein I (beta 2 GPI), have been examined for effects on the activation of factor X by tissue factor-factor VIIa. In these experiments, bovine tissue factor, reconstituted into phosphatidylserine-phosphatidylcholine (PS/PC; 30/70) vesicles, was used at a single concentration while factor X (the substrate), factor VIIa (the enzyme), and the potentially inhibitory proteins were varied in a continuous chromogenic assay. Apo A-II and CRP clearly inhibit tissue factor-factor VIIa activation of factor X, while apo A-I and beta 2 GPI have little or no effect. These results demonstrate that different lipid binding proteins vary in their effects on tissue factor activity.
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism; D002352:Carrier Proteins / Q000097:blood*; D005167:Factor VII / Q000378:metabolism*; D015942:Factor VIIa; D005170:Factor X / Q000378:metabolism*; D006023:Glycoproteins / Q000097:blood; D006801:Humans; D008055:Lipids / Q000097:blood*; D053482:beta 2-Glycoprotein I
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A; D002352:Carrier Proteins; D006023:Glycoproteins; D008055:Lipids; D053482:beta 2-Glycoprotein I; D005167:Factor VII; D005170:Factor X; D002097:C-Reactive Protein; D015942:Factor VIIa