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QuickView for Alpha carbonic anhydrase domain superfamily (biogroup)
- Description:
- This entry represents a domain characteristic of alpha class carbonic anhydrases. The dominating secondary structure is a 10-stranded, twisted beta-sheet, which divides the molecules into two halves. Alpha-CAs contain a single zinc atom bound to three conserved histidine residues. The catalytically active group is the zinc-bound water which ionizes to a hydroxide group. In the mechanism of catalysis, nucleophilic attack of CO2 by a zinc-bound hydroxide ion is followed by displacement of the resulting zinc-bound bicarbonate ion by water; subsequent deprotonation regenerates the nucleophilic zinc-bound hydroxide ion.A carbonic anhydrase-like domain with striking homology to that of the alpha class carbonic anhydrases is also found in receptor-type tyrosine-protein phosphatase gamma and zeta. In this case it may have a different function, as only one of the three His residues that ligate the zinc atom and are required for catalytic activity is conserved.Carbonic anhydrases (CA: ) are zinc metalloenzymes which catalyse the reversible hydration of carbon dioxide to bicarbonate. 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).
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