title: Degradation of factor VIII coagulant antigen by proteolytic enzymes.
abstract: The factors responsible for the lability of factor VIII coagulant activity (VIII:C) and factor VIII coagulant antigen (VIII:CAg) are poorly understood. In this study the VIII:C and VIII:CAg are studied after incubation with plasmin, trypsin or alpha-chymotrypsin. Both isolated human VIII:CAg and VIII:CAg associated with factor VIII-related antigen (VIII R:Ag) are evaluated. The antigenic sites of the VIII:CAg are somewhat more stable to the action of these enzymes than the functional activity, although both follow a generally parallel degradation. A biphasic decay curve is seen in the initial time points. No stabilization of the functional or antigenic reactivity is observed in the presence of the VIII R:Ag. Lower concentrations of each enzyme cause an initial rise in the factor VIII:C in the presence of VIII R:Ag, but not in the isolated VIII:CAg. Higher concentrations of alpha-chymotrypsin cause activation of VIII:C and a slight decrease in the VIII:CAg values in both preparations. These enzymes may play a modulating role in the coagulation cascade through the activation and degradation of VIII:C and VIII:CAg.
authors.forename: M E
authors.initials: ME
authors.lastname: Rick
authors.forename: M A
authors.initials: MA
authors.lastname: Popovsky
authors.forename: D M
authors.initials: DM
authors.lastname: Krizek
mesh_terms: D000937:Antigen-Antibody Reactions / Q000187:drug effects; D000941:Antigens / Q000276:immunology; D002918:Chymotrypsin / Q000494:pharmacology; D005169:Factor VIII / Q000276:immunology*; D005341:Fibrinolysin / Q000494:pharmacology; D006801:Humans; D010447:Peptide Hydrolases / Q000494:pharmacology*; D014357:Trypsin / Q000494:pharmacology; D014841:von Willebrand Factor
chemical_list: D000941:Antigens; D014841:von Willebrand Factor; D005169:Factor VIII; D010447:Peptide Hydrolases; D002918:Chymotrypsin; D014357:Trypsin; D005341:Fibrinolysin