InterPro domain: IPR001765

Carbonic anhydrases ( 4.2.1.1 ) (CA) are zinc metalloenzymes which catalyze the reversible hydration of carbon dioxide.In Escherichia coli, CA (gene cynT) is involved in recycling carbon dioxide formed in the bicarbonate-dependent decomposition of cyanate by cyanase (gene cynS). By this action, it prevents the depletion of cellular bicarbonate [ 1 ]. In photosynthetic bacteria and plant chloroplast, CA is essential to inorganic carbon fixation [ 2 ].Prokaryotic and plant chloroplast CA are structurally and evolutionary related and form a family distinct from the one which groups the many different forms of eukaryotic CA's (see IPR001148 ).

This family also includes the carbonyl sulfide hydrolase from Thiobacillus thioparus which responsible for the degradation of carbonyl sulfide to hydrogen sulfide and CO2, the second step of SCN(-) assimilation [ 3 ], and a carbon disulfide hydrolase from acidothermophilic archaeon Acidianus, which has a typical carbonic anhydrase fold and active site but does not use CO2 as a substrate [ 4 ].

1. Carbonic anhydrase in Escherichia coli. A product of the cyn operon. J. Biol. Chem. 267, 3731-4
2. A gene homologous to chloroplast carbonic anhydrase (icfA) is essential to photosynthetic carbon dioxide fixation by Synechococcus PCC7942. Proc. Natl. Acad. Sci. U.S.A. 89, 4437-41
3. Carbonyl Sulfide Hydrolase from Thiobacillus thioparus Strain THI115 Is One of the β-Carbonic Anhydrase Family Enzymes. J. Am. Chem. Soc. 135, 3818-25
4. Evolution of a new enzyme for carbon disulphide conversion by an acidothermophilic archaeon. Nature 478, 412-6