title: Role of heparin in the interaction of serine proteinases with antithrombin III.
abstract: To characterize the mode of action of heparin, the kinetics of inhibition of thrombin, factor Xa, and plasmin by antithrombin III was studied without and in the presence of heparin. Following the concentration dependence of inactivation a linear dependence was found between the apparent first-order inactivation rate constant and the anti-thrombin III concentration. This behaviour is typical of enzyme-activator interaction. Values of kinetic constants of the inactivation reaction could be determined. Thus, heparin acts obviously as an activator of the enzymes and enhances their affinity for antithrombin III.
mesh_terms: D000990:Antithrombin III; D010450:Endopeptidases; D005170:Factor X; D005341:Fibrinolysin; D006493:Heparin; D007700:Kinetics; D008433:Mathematics; D011485:Protein Binding; D012694:Serine; D013917:Thrombin
chemical_list: D012694:Serine; D000990:Antithrombin III; D005170:Factor X; D006493:Heparin; D010450:Endopeptidases; D013917:Thrombin; D005341:Fibrinolysin