InterPro : IPR023561

Name  Carbonic anhydrase, alpha-class Short Name  Carbonic_anhydrase_a-class
Type  Family Description  Carbonic anhydrases (CA: ) are zinc metalloenzymes which catalyse the reversible hydration of carbon dioxide to bicarbonate [, ]. CAs have essential roles in facilitating the transport of carbon dioxide and protons in the intracellular space, across biological membranes and in the layers of the extracellular space; they are also involved in many other processes, from respiration and photosynthesis in eukaryotes to cyanate degradation in prokaryotes. There are five known evolutionarily distinct CA families (alpha, beta, gamma, delta and epsilon) that have no significant sequence identity and have structurally distinct overall folds. Some CAs are membrane-bound, while others act in the cytosol; there are several related proteins that lack enzymatic activity. The active site of alpha-CAs is well described, consisting of a zinc ion coordinated through 3 histidine residues and a water molecule/hydroxide ion that acts as a potent nucleophile. The enzyme employs a two-step mechanism: in the first step, there is a nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide; in the second step, the active site is regenerated by the ionisation of the zinc-bound water molecule and the removal of a proton from the active site []. Beta- and gamma-CAs also employ a zinc hydroxide mechanism, although at least some beta-class enzymes do not have water directly coordinated to the metal ion. The alpha-CAs are found predominantly in animals but also in bacteria and green algae. There are at least 15 isoforms found in mammals, which can be subdivided into cytosolic CAs (CA-I, CA-II, CA-III, CA-VII and CA XIII), mitochondrial CAs (CA-VA and CA-VB), secreted CAs (CA-VI), membrane-associated (CA-IV, CA-IX, CA-XII and CA-XIV) and those without CA activity, the CA-related proteins (CA-RP VIII, X and XI).The beta-CAs are highly abundant in plants, diatoms, eubacteria and archaea [, ]. The beta-CAs are far more diverse in sequence than other classes, and can be divided into different clades based on sequence identity, with the plant enzymes forming two clades representing dicotyledonous and monocotyledonous plants. Characterisation of these enzymes reveals sharp differences between the beta class, which forms dimers, tetramers, hexamers and octomers, and the alpha and gamma classes, which form strictly monomers and trimers. The gamma-CAs may be the most ancient form of carbonic anhydrases, having evolved long before the alpha class, to which it is more closely related than to the beta-class [, ]. The reaction mechanism of the gamma-class is similar to that of the alpha-class, even though the overall folds are dissimilar and the active site residues differ. The delta-CAs are found in marine algae and dinoflagellates []. The epsilon-CAs are found in prokaryotes such as Thiobacillus neapolitanus(Halothiobacillus neapolitanus) in which it is a component of the carboxysome shell, where it could supply the active sites of RuBisCO in the carboxysome with the high concentrations of carbon dioxide necessary for optimal RuBisCO activity and efficient carbon fixation [].This entry represents alpha class carbonic anhydrases.

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



15 Child Features

Id Name Short Name Type
IPR018443 Carbonic anhydrase 2 CA2 Family
IPR018426 Carbonic anhydrase, CA15 Carbonic_anhydrase_CA15 Family
IPR018438 Carbonic anhydrase, CA-VII Carbonic_anhydrase_CA7 Family
IPR018428 Carbonic anhydrase, CA-VI Carbonic_anhydrase_CA6 Family
IPR018343 Carbonic anhydrase, CA4 Carbonic_anhydrase_CA4 Family
IPR018347 Putative carbonic anhydrase-like protein 2 CAH2 Family
IPR018442 Carbonic anhydrase, CA1 Carbonic_anhydrase_CA1 Family
IPR018441 Carbonic anhydrase, CA3 Carbonic_anhydrase_CA3 Family
IPR018429 Carbonic anhydrase 9 CA9 Family
IPR018423 Carbonic anhydrase-related protein 10 CA10 Family
IPR018431 Carbonic anhydrase, CA14 Carbonic_anhydrase_CA14 Family
IPR018430 Carbonic anhydrase, CA-XII Carbonic_anhydrase_CA12 Family
IPR018437 Carbonic anhydrase VB, mitochondria CA-VB_mt Family
IPR018433 Carbonic anhydrase, putative, insect Carbonic_anhydrase_put_insect Family
IPR018434 Carbonic anhydrase-related protein, CA8 Carbonic_anhydrase_RP_CA8 Family

0 Contains

0 Found In

0 Parent Features

9 Publications

First Author Title Year Journal Volume Pages
So AK A novel evolutionary lineage of carbonic anhydrase (epsilon class) is a component of the carboxysome shell. 2004 J Bacteriol 186 623-30
Lindskog S Structure and mechanism of carbonic anhydrase. 1997 Pharmacol Ther 74 1-20
Supuran CT Carbonic anhydrases--an overview. 2008 Curr Pharm Des 14 603-14
Smith KS Prokaryotic carbonic anhydrases. 2000 FEMS Microbiol Rev 24 335-66
Sawaya MR The structure of beta-carbonic anhydrase from the carboxysomal shell reveals a distinct subclass with one active site for the price of two. 2006 J Biol Chem 281 7546-55
Smith KS Roles of the conserved aspartate and arginine in the catalytic mechanism of an archaeal beta-class carbonic anhydrase. 2002 J Bacteriol 184 4240-5
Fu X Evolution of structure in gamma-class carbonic anhydrase and structurally related proteins. 2008 Mol Phylogenet Evol 47 211-20
Zimmerman SA The beta and gamma classes of carbonic anhydrase. 2008 Curr Pharm Des 14 716-21
Lapointe M An external delta-carbonic anhydrase in a free-living marine dinoflagellate may circumvent diffusion-limited carbon acquisition. 2008 Plant Physiol 147 1427-36

To cite PlanMine, please refer to the following publication:

Rozanski, A., Moon, H., Brandl, H., Martín-Durán, J. M., Grohme, M., Hüttner, K., Bartscherer, K., Henry, I., & Rink, J. C.
PlanMine 3.0—improvements to a mineable resource of flatworm biology and biodiversity
Nucleic Acids Research, gky1070. doi:10.1093/nar/gky1070 (2018)