Pyrrole Hydrogen Ionization of Imidazole Derivatives in Metal Ion Complexes and Carbonic Anhydrase

  1. R. Bruce Martin
  1. 1Chemistry Department, University of Virginia, Charlottesville, Va. 22901

Abstract

Zinc ion-induced pyrrole hydrogen ionization from a histidyl residue has recently been suggested as the source of the activity-related deprotonation in carbonic anhydrase (EC 4.2.1.1; carbonate hydro-lyase) occurring at pH 7-8. The results offered to support the hypothesis are shown to be deficient. Examination of the literature reveals no precedent for such a pronounced acidification from pKa [unk] 14.2 in imidazole compounds by zinc ion. It is suggested that Zn(II)-induced pyrrole ionizations in imidazoles occur with pKa about 13.

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  1. PNAS November 1, 1974 vol. 71 no. 11 4346-4347
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