The enzyme Carbonic anhydrase II having an accession number of NP_414668 is also called carbonate dehydratase which is part of the enzyme family that catalyses rapid inter-conversion of carbon dioxide & water to bicarbonate， carbonic acid and protons（CO2 + H2O ? HCO3? + H+)， a reaction that occurs rather slowly in the absence of a catalyst. The majority of carbonic anhydrases enclose a zinc ion in their active site and therefore is classified as metalloenzymes.
The most important function of Carbonic anhydrase is known to preserve acid-base balance in blood and other tissues， and to help transport carbon dioxide of tissues. Carbonic anhydrases have been found in all kingdoms of life. Carbonic anhydrase has 3 different classes: alpha， beta and gamma which share very little sequence or structural similarity， thus far they all perform the same function and require a zinc ion at the active site. Mammalian carbonic anhydrase is monomeric and belongs to the alpha class. Plant carbonic anhydrase is dimeric and belongs to the beta class.
Methane-producing bacteria carbonic anhydrase is trimeric and grows in hot springs which forms the gamma class.
