Carbonic anhydrase II (CAII) is a single polypeptide chain of molecular weight 29kDa. It is present in the cytosol of most tissues, but highest concentrations are found, like Carbonic Anhydrase I, in erythrocytes. The concentration in erythrocytes is about 20µM. It catalyses the hydration of CO2 and the hydrolysis of esters. Zn2+ ion cofactor is required for enzyme activity. Certain point mutations occur without apparent clinical effect, however, complete absence leads to mild mental reta