Carbonic anhydrase (CA) is a seemingly ubiquitous enzyme of profound physiological importance, which plays essential roles in respiration, acid-base homeostasis, bone resorption, calcification, photosynthesis, several biosynthetic pathways and a variety of processes involving ion, gas and fluid transfer. This enzyme, which is present in at least three gene families (a, ss, ?), has found favour as a model for the study of evolution of gene families and for site-directed mutagenesis in structure/function relationships, for protein folding and for transgenic and gene target studies. Since the...