Carbonic anhydrase - a universal enzyme of the carbon-based life

Carbonic anhydrase (CA) is a metalloenzyme that performs interconversion between CO2 and the bicarbonate ion (HCO3 -). CAs appear among all taxonomic groups of three domains of life. Wide spreading of CAs in nature is explained by the fact that carbon, which is the major constituent of the enzyme's substrates, is a key element of life on the Earth. Despite the diversity of CAs, they all carry out the same reaction of CO2/HCO3 - interconversion. Thus, CA obviously represents a universal enzyme of the carbon-based life. Within the classification of CAs, here we proposed the existence of an extensive family of CA-related proteins (γCA-RPs)-the inactive forms of γ-CAs, which are widespread among the Archaea, Bacteria, and, to a lesser extent, in Eukarya. This review focuses on the history of CAs discovery and integrates the most recent data on their classification, catalytic mechanisms, and physiological roles at various organisms.