Journal of Protein Chemistry

, Volume 3, Issue 4, pp 357–367 | Cite as

Inhibition by cupric ions of the hydration of CO2 catalyzed by carbonic anhydrase II

  • T. Kararli
  • D. N. Silverman


The inhibition by cupric ions of the hydration of CO2 catalyzed by carbonic anhydrase II is interesting because of the results of Tuet al. obtained at chemical equilibrium, indicating that Cu2+ inhibits specifically a proton transfer in the catalytic pathway. We have measured this inhibition at steady state, using stopped-flow methods. The inhibition by Cu2+ of the hydration of CO2 catalyzed by carbonic anhydrase II had aK I near 1×10−6 M atpH 7.0 and gave inhibition that is noncompetitive atpH 6.0 and mixed, but close to uncompetitive, atpH 6.8. ThepH dependence of this binding is consistent with a binding site for Cu2+ on the enzyme with apK a near 7. The binding interaction between Cu2+ and the fluorescent inhibitor 5-dimethylaminonaphthalene-l-sulfonamide on carbonic anhydrase II was noncompetitive, indicating that the binding site for Cu2+ is distinct from the coordination sphere of zinc in which the actual interconversion of CO2 and HCO 3 and the binding of sulfonamides takes place.

Key words

carbonic anhydrase mechanism of catalysis inhibition copper 


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Copyright information

© Plenum Publishing Corporation 1984

Authors and Affiliations

  • T. Kararli
    • 1
  • D. N. Silverman
    • 1
  1. 1.Department of PharmacologyUniversity of FloridaGainesville

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