title: Protection of platelet surface bound factors IXa and VIII against specific inhibitors.
abstract: The rate of inactivation of factors IXa and VIII as well as of the complex formed by them on the surface of platelets, induced by specific inhibitors has been studied. After the formation of complex both factors became more protected against high molecular weight inhibitors. As evidenced by the apparent first order inactivation rate constants, after complex formation the velocity of IXa-antithrombin III + heparin reaction decreased  to 1/20. Enhanced resistance toward the high molecular weight inhibitors is presumably due to a steric change, since the low molecular weight phenylmethyl sulfonyl fluoride and diethyl pyrocarbonate inhibited free and complexed factor IXa to the same extent.
mesh_terms: D000906:Antibodies; D000990:Antithrombin III / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D005164:Factor IX / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015949:Factor IXa; D005167:Factor VII / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology
chemical_list: D000906:Antibodies; D010664:Phenylmethylsulfonyl Fluoride; D000990:Antithrombin III; D005167:Factor VII; D005164:Factor IX; D015949:Factor IXa; D004047:Diethyl Pyrocarbonate