Characterization of a high activity carbonic anhydrase isozyme purified from erythrocytes of Salmo gairdneri

Abstract

1. 1. A single, high specific activity carbonic anhydrase (CA) isozyme was present in erythrocytes of the teleostean species Salmo gairdneri (rainbow trout). 2. 2. Purification of trout CA to homogeneity was accomplished using chloroform-ethanol extraction, Sephadex G-75 gel filtration, and DEAE Bio-Gel anion exchange chromatography. 3. 3. Trout CA was a zinc metalloenzyme of mol. wt 28,300 and pl 9.3. 4. 4. Amino acid analysis indicated the presence of 6 half-cystine residues per enzyme molecule, and the presence of a sulfhdryl reducing agent was required to maintain full activity in vitro. 5. 5. Sulfhydryl modification with both N-ethylmaleimide and acrylonitrile indicated the presence of 3 reactive sulfhydryl groups per CA molecule. Modification of those groups had no direct effect on enzyme activity, but modified CA was no longer subject to inactivation by oxidizing conditions.