Molecular evolution and selection pressure in alpha-class carbonic anhydrase family members

► Zinc binding residues are under strong purifying selection in all CA isozymes. ► Apossible second CO2 binding site on the surface of CA II and CA XIII is supported. ► The CA II - ICA interface likely includes His4, Phe20, Ser73, Ser166, and Gly171. ► The predicted AE1 binding site for CA II is strongly conserved. ► Potential protein interface sites for CA VI are identified.