Kinetic mechanism of protease inhibition by α 1-antitrypsin

Un Beom Kang, Je Hyun Baek, Seung Hyun Ryu, Joon Kim, Myeong Hee Yu, Cheolju Lee

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


The native form of serine protease inhibitor (serpin) is kinetically trapped in a metastable state. Metastability in these proteins is critical to inhibit target protease by forming a stable covalent complex. Despite recent determination of the crystal structures of a Michaelis protease-serpin complex as well as a stable covalent complex, details on the kinetic mechanism remain unsolved. In this report, we examined the reaction mechanism of α 1-antitrypsin toward elastase by a combination of stopped-flow experiments via fluorescence resonance energy transfer and rapid-quench studies. The results suggest a non-covalent complex intermediate other than Michaelis complex as an intermediate before the cleavage of P1-P1′ scissile bond, whose formation is the rate-determining step of the overall reaction. This rate-limiting step represents rearrangement of the reactive site loop, and is regulated by a salt bridge between E354 and R196. The ionic interaction is unique to α 1-antitrypsin, which suggests that protease inhibition mechanisms are varied among serpins.

Original languageEnglish
Pages (from-to)409-415
Number of pages7
JournalBiochemical and biophysical research communications
Issue number2
Publication statusPublished - 2004 Oct 15


  • Acyl intermediate
  • Rapid-quench study
  • Rate-determining step
  • Salt bridge
  • Serpin
  • Stopped-flow experiment
  • α -Antitrypsin

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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