PURIFICATION AND PARTIAL CHARACTERIZATION OF HIGH AND LOW ACTIVITY CARBONIC-ANHYDRASE ISOENZYMES FROM MALACLEMYS-TERRAPIN-CENTRATA

High activity (CA C) and low activity (CA B) carbonic anhydrase [EC 4.2.1.1] isoenzymes were purified from diamondback terrapin erythrocytes. The 2 isoenzymes differed in CO2 hydration specific activity by 36-fold. The low activity isoenzyme contained one half-cystine residue, whereas the high activity isoenzyme contained 4 half-cystines and required a reducing environment to maintain activity. Both isoenzymes contained Zn. MW of 28,500 and 30,400 daltons were established for the low and high activity isoenzymes, respectively. Both isoenzymes were inhibited by parachloromercuribenzoate. The low activity isoenzyme was present in the erythrocytes at about 8-10 times the concentration of the high activity isoenzyme. The high activity isoenzyme cross-reacted with antibodies prepared against pure chicken carbonic anhydrase C.