Carbonic anhydrase, alpha-class, conserved site
IPR018338
Definition
Carbonic anhydrases (CA: [ec:4.2.1.1]) are zinc metalloenzymes which catalyse the reversible hydration of carbon dioxide to bicarbonate [[cite:PMID:18336305], [cite:PMID:10978542]]. 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 PMID:9336012. 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. This entry represents a conserved site based around one of the zinc-binding histidines in the alpha class of carbonic anhydrases.
12 human proteins with this domain
Each is a reviewed human protein in the Seroatlas serome and a potential autoantibody target; this domain groups them into one antibody-relevant category. Every entry links to its own record.
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