title: Plasmin-mediated activation and inactivation of thrombin-activatable fibrinolysis inhibitor.
abstract: Activated thrombin-activatable fibrinolysis inhibitor (TAFIa) attenuates the fibrin cofactor function of tissue-type plasminogen activator-mediated plasmin formation and subsequently fibrin degradation. In the present study, we focused on the role of plasmin in the regulation of TAFIa activity. Upon incubation with plasmin, TAFIa activity was generated, which was unstable at 37 degrees C. Analysis of the cleavage pattern showed that TAFI was cleaved at Arg(92), releasing the activation peptide from the 35.8-kDa catalytic domain. The presence of the 35.8-kDa fragment paralleled the time course of generation and loss of TAFIa activity. This suggested that, in the presence of plasmin, TAFIa is probably inactivated by proteolysis rather than by conformational instability. TAFI was also cleaved at Arg(302), Lys(327), and Arg(330), resulting in a approximately 44.3-kDa fragment and several smaller fragments. The 44.3-kDa fragment is no longer activatable since it lacks part of the catalytic center. We concluded that plasmin can cleave at several sites in TAFI and that this contributes to the regulation of TAFI and TAFIa.
authors.affiliation: Thrombosis and Haemostasis Laboratory, Department of Haematology, University Medical Centre, P.O. Box 85500, 3508 GA Utrecht, The Netherlands. P.F.Marx@amc.uva.nl
authors.forename: Pauline F
authors.initials: PF
authors.lastname: Marx
authors.forename: Philip E
authors.initials: PE
authors.lastname: Dawson
authors.forename: Bonno N
authors.initials: BN
authors.lastname: Bouma
authors.forename: Joost C M
authors.initials: JC
authors.lastname: Meijers
mesh_terms: D025901:Carboxypeptidase B2 / Q000302:isolation & purification / Q000378:metabolism*; D020134:Catalytic Domain / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation; D004795:Enzyme Stability / Q000502:physiology; D005341:Fibrinolysin / Q000378:metabolism*; D006801:Humans; D010446:Peptide Fragments / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D010446:Peptide Fragments; D010447:Peptide Hydrolases; D025901:Carboxypeptidase B2; D005341:Fibrinolysin