Gamma carbonic anhydrases (CA): Carbonic anhydrases are zinc-containing enzymes that catalyze the reversible hydration of carbon dioxide in a two-step mechanism, involving the nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide, followed by the regeneration of the active site by ionization of the zinc-bound water molecule and removal of a proton from the active site. They are ubiquitous enzymes involved in fundamental processes like photosynthesis, respiration, pH homeostasis and ion transport. There are three distinct groups of carbonic anhydrases - alpha, beta and gamma - which show no significant sequence identity or structural similarity. Gamma CAs are homotrimeric enzymes, with each subunit containing a left-handed parallel beta helix (LbH) structural domain.
Comment:Active gamma carbonic anhydrase is trimeric, with active sites located at the interface between two LbH subunits. The trimer structure contains three active sites and each subunit contributes to two active sites via residues located on two surfaces.
Comment:Carbonic anhydrases catalyze the reversible hydration of carbon dioxide through a two-step mechanism involving the nucleophilic attack of a zinc-bound hydroxide ion on carbon dioxide, followed by the regeneration of the active site by ionization of the zinc-bound water molecule and removal of a proton from the active site.
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