InterPro domain: IPR036874

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 ]. CA has a resolvase-like fold, which has a core structure composed of three layers (alpha/beta/alpha) arranged in mixed beta-sheet of five strands where strand 5 is antiparallel to the rest.Prokaryotic and plant chloroplast CA are structurally and evolutionary related and form a superfamily distinct from the one which groups the many different forms of eukaryotic CA's (see IPR036398 ).

This superfamily also includes the Bacillus subtilis protein YbcF that does not seem to be able to bind zinc, which all carbonic anhydrases are thought to require, and a carbon disulfide hydrolase from acidothermophilic archaeon Acidianus, which has a typical carbonic anhydrase fold and active site but does not use CO(2) as a substrate [ 3 ].

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. Evolution of a new enzyme for carbon disulphide conversion by an acidothermophilic archaeon. Nature 478, 412-6