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Human procarboxypeptidase U, or thrombin-activable fibrinolysis inhibitor, is a substrate for transglutaminases. Evidence for transglutaminase-catalyzed cross-linking to fibrin

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  • Interdisciplinary Nanoscience Center
  • Department of Molecular Biology
Procarboxypeptidase U (EC 3.4.17.20) (pro-CpU), also known as plasma procarboxypeptidase B and thrombin-activable fibrinolysis inhibitor, is a human plasma protein that has been implicated in the regulation of fibrinolysis. In this study, we show that pro-CpU serves as a substrate for transglutaminases. Both factor XIIIa and tissue transglutaminase catalyzed the polymerization of pro-CpU and the cross-linking to fibrin as well as the incorporation of 5-dimethylaminonaphthalene-1-sulfonyl cadaverine (dansylcadaverine), [14C]putrescine, and dansyl-PGGQQIV. These findings show that pro-CpU contains both amine acceptor (Gln) and amine donor (Lys) residues. The amine acceptor residues were identified as Gln2, Gln5, and Gln292, suggesting that both the activation peptide and the mature enzyme participate in the cross-linking reaction. These observations imply that transglutaminases may mediate covalent binding of pro-CpU to other proteins and cell surfaces in vivo. In particular, factor XIIIa may cross-link pro-CpU to fibrin during the latter part of the coagulation cascade, thereby helping protect the newly formed fibrin clot from premature plasmin degradation. Moreover, the cross-linking may facilitate the activation of pro-CpU, stabilize the enzymatic activity, and protect the active enzyme from further degradation.
Original languageEnglish
JournalJournal of Biological Chemistry
Volume273
Issue42
Pages (from-to)27220-4
Number of pages4
ISSN0021-9258
Publication statusPublished - 1998

    Research areas

  • Binding Sites, Blood Coagulation, Carboxypeptidase U, Carboxypeptidases, Cross-Linking Reagents, Enzyme Activation, Enzyme Precursors, Fibrin, Glutamine, Humans, Substrate Specificity, Transglutaminases

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