Structure and catalytic mechanism of the β-carbonic anhydrases

The beta-carbonic anhydrases (beta-CAs) are a diverse but structurally related group of zinc-metalloenzymes found in eubacteria, plant chloroplasts, red and green algae, and in the Archaea. The enzyme catalyzes the rapid interconversion of CO2 and H2O to HCO3- and H+, and is believed to be associated with metabolic enzymes that consume or produce CO2 or HCO3. For many organisms, beta-CA is essential for growth at atmospheric concentrations of CO2- Of the five evolutionarily distinct classes of carbonic anhydrase, beta-CA is the only one known to exhibit allosterism. Here we review the structure and catalytic mechanism of beta-CA including the structural basis for allosteric regulation. (C) 2009 Elsevier B.V. All rights reserved.