“…Based on their structural features, they are grouped into seven different classes, namely a-, b-, c-, d-, f-, g-and h-CAs. a-CAs are predominantly expressed in vertebrates, bacteria, algae and cytoplasm of green plants, b-CAs in bacteria, algae and chloroplasts, c-CAs in archaea and some bacteria, d-and f-CAs in some marine diatoms, g-CAs only in the protozoan parasite Plasmodium spp., whereas the recently discovered h-class has been so far found only into the marine diatom Phaeodactylum tricornutum [1][2][3][4][5][6][7][8] . Humans encode 12 catalytically active a-CA isozymes, which differ in molecular features, oligomeric arrangement, kinetic properties and cellular localisation, with isoforms I, II, III, VII and XIII localised in the cytosol, CA IV, IX, XII and XIV associated with the cell membrane, CA VA and VB confined in mitochondria, and CA VI secreted in saliva and milk 1 .…”