Molecular Pharmacology, Vol 10, 335-343, Copyright © 1974 by the American Society for Pharmacology and Experimental Therapeutics

The Isolation and Partial Characterization of Sulfonamide-Resistant Carbonic Anhydrases from the Liver of the Male Rat

¹ Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, Florida 32610

The liver of the adult male rat contains carbonic anhydrase activity which is 10,000 times less sensitive to inhibition by acetazolamide than the carbonic anhydrase present in female rat liver or canine liver from either sex, or in rat kidney or erythrocytes from either sex. By contrast, inhibition of the carbonic anhydrase activity from the livers of male rats by cyanide or bisulfide anions occurs with I₅₀ values similar to those of rat erythrocyte carbonic anhydrase. Using standard biochemical techniques, we have shown that the activity exists as four isoenzymatic forms, consisting of two major and two minor species. The two major species have been isolated, and run as single bands on polyacrylamide gel electrophoresis. They both have a molecular weight of approximately 29,000, as determined by molecular sieve chromatography, and probably contain 1 atom of zinc per molecule. The enzymes retain their resistance to inhibition by acetazolamide throughout the isolation procedure. The turnover number is about 3300 sec^-1, roughly 1% of that of human red cell carbonic anhydrase C and most tissue carbonic anhydrases.

Note:
ACKNOWLEDGMENT We wish to thank Dr. Joseph E. Coleman of Yale University for carrying out the zinc determinations.