Fibrinolysis is amplified by converting α2-antiplasmin from a plasmin inhibitor to a substrate

I. Y. Sazonova, B. M. Thomas, I. P. Gladysheva, A. K. Houng, Guy L. Reed

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


α2-antiplasmin (α2-AP) is the fast serpin inhibitor of plasmin and appears to limit the success of treatment for thrombosis. We examined the mechanisms through which monoclonal antibodies (mAbs) against α2-AP amplify fibrinolysis. The mAbs RWR, 49 and 77 interfered with the ability of α2-AP to inhibit plasmin, microplasmin and trypsin. In solution, mAbs 49 and 77 bound to α2-AP with 5-fold to 10-fold higher relative affinity than mAb-RWR, while mAb-RWR bound with greater avidity to immobilized or denatured α2-AP. Binding studies with chimeric α2-APs revealed that none of the mAbs bound to sites in α2-AP that form putative contacts with plasmin, namely the carboxy terminal lysines of α2-AP, or the reactive center loop in the serpin domain of α2-AP. Rather, mAb-RWR recognized an epitope in the amino-terminus of α2-AP (L 13 GNQEPGGQTALKSPPGVCS 32) near the site at which α2-AP cross-links to fibrin. mAbs 49 and 77 bound to another conformational epitope in the serpin domain of α2-AP. mAbs 49 and 77 markedly increased the stoichiometry of plasmin inhibition by α2-AP (from 1.1 ± 0.1 to 51 ± 4 and 67 ± 7) indicating that they convert α2-AP from an inhibitor to a substrate of plasmin. This was confirmed by sodium dodecylsulfate polyacrylamide gel electrophoresis analysis showing cleavage of α2-AP by plasmin in the presence of these mAbs. In summary, these mAbs appear to act at sites distinct from known α2-AP-plasmin contacts to enhance fibrinolysis by converting α2-AP from an inhibitor to a plasmin substrate.

Original languageEnglish (US)
Pages (from-to)2087-2094
Number of pages8
JournalJournal of Thrombosis and Haemostasis
Issue number10
StatePublished - Oct 2007
Externally publishedYes


  • Antiplasmin
  • Fibrinolysis
  • Inhibition
  • Plasminogen activation

ASJC Scopus subject areas

  • Hematology


Dive into the research topics of 'Fibrinolysis is amplified by converting α2-antiplasmin from a plasmin inhibitor to a substrate'. Together they form a unique fingerprint.

Cite this