The sequestration of hydroxyl ions by C2 in liquid water: useful physiological roles for a reversible complex formation in the presence of protein catalysts.
A second function of carbonic anhydrase (CA) isoforms has already been proposed. This involves the dispersal of complexes in which six carbon dioxide molecules sequester a hydroxyl ion when the gas reacts with liquid water. The semi-catalytic reaction does not require the formation of bicarbonate as an essential corollary. This function is, therefore, a likely activity of carbonic anhydrase related proteins that have recently been discovered and which lack the active zinc site essential for the hydration of carbon dioxide. Re-examination of possible functions for the complex of six CO2 molecules with a hydroxyl anion have brought to light several circumstances where the presence of fully reversible complexes could have physiological advantages. A catalytic synthesis and dissolution of the complexes could thus be the important function for the carbonic anhydrase-related proteins (CA-RP) molecules as well as of some CA isoforms. The possible mechanisms for this extended second catalytic function and examples are briefly discussed.
Widdas
W F
WF
Department of Biological Sciences, Royal Holloway College, University of London, Egham, Surrey, Great Britain.
Baker
G F
GF
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001834:Body Water / Q000737:chemistry; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry*; D002256:Carbonic Anhydrases / Q000737:chemistry*; D004734:Energy Metabolism / Q000502:physiology; D004912:Erythrocytes / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D009124:Muscle Proteins / Q000737:chemistry; D009419:Nerve Tissue Proteins / Q000737:chemistry; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009995:Osmosis / Q000502:physiology; D014867:Water / Q000737:chemistry*
D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D014867:Water; D002245:Carbon Dioxide; D017665:Hydroxyl Radical; D002256:Carbonic Anhydrases