Regulation of the Activity of Lysosomal Cysteine Proteinases by pH-lnduced Inactivation and/or Endogenous Protein Inhibitors, Cystatins

  • Turk, Boris
  • Bieth, Joseph G.
  • Björk, Ingemar
  • Dolenc, Iztok
  • Turk, Dušan
  • Cimerman, Nina
  • Kos, Janko
  • Čolič, Adrijana
  • Stoka, Veronika
  • Turk, Vito

  • 1 Dept. Biochemistry and Molecular Biology, J. Stefan Institute, Jamova 39,61 000 Ljubljana, Slovenia

    2 Dept. Veterinary Medical Chemistry, The Biomedical Center, POB 575, S-751 23 Uppsala, Sweden

    3 INSERM U392, Universite Louis Pasteur de Strasbourg, 74 Route du Rhin, F-67 400 Illkirch, France

    4 Krka Pharmaceuticals, 68 000 Novo Mesto, Slovenia

* Corresponding author

a Correspondence address: Dept. Veterinary Medical Chemistry, The Biomedical Center, POB 575, S-751 23 Uppsala, Sweden.

Received December 5, 1994; accepted February 13, 1995

Biological Chemistry 376(4):p 225-230, April 1995.

The kinetics of pH-induced inactivation of human cathepsins B and L was studied by conventional and stopped-flow methods. The inactivation of both enzymes was found to be an irreversible, first-order process. The inactivation rate constants increased exponentially with pH for both enzymes. From logkinacvspH plots, 3.0 and 1.7 protons were calculated to be desorbed for pH-induced inactivation of cathepsins L and B. Cathepsin B was thus substantially more stable than cathepsin L (˜ 15-fold at pH 7.0 and 37 °C). Cathepsin B was efficiently inhibited by cystatin C at pH 7.4, whereas the inhibition by stefin B and high molecular weight kininogen was only moderate. In contrast, cathepsin L was efficiently inhibited by both chicken cystatin and stefin B at this pHkass ˜ 3.3 × 107 m-1 s-1).

Copyright © 1995 Walter de Gruyter