volume 32, issue 40, P10757-10762 1993
DOI: 10.1021/bi00091a029
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David N. Silverman, Chingkuang Tu, Xian Chen, Susan M. Tanhauser, A. Jerry Kresge, Philip J. Laipis

Abstract: Maximal turnover rates for the dehydration of HCO3- catalyzed by the zinc metalloenzyme carbonic anhydrase III are limited by a proton transfer to zinc-bound hydroxide in the active site. We have used site-directed mutagenesis to place a proton donor, histidine, at position 64 and used 18O exchange between CO2 and water measured by mass spectrometry to determine the rates of intramolecular proton transfer to the zinc-bound hydroxide. In a series of site-specific mutants, the values of pKa of the zinc-bound wat…

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