title: A search for the function of human carbonic anhydrase B.
abstract: Because of the very high activity and abundance of human red cell carbonic anhydrase C (carbamate hydrolase, EC 4.2.1.1), it seemed likely that the second isozyme, B, might not be essential for CO2 metabolism. It was then found that physiological concentrations of Cl- inhibited catalysis of CO2 hydration by the B enzyme (but not by type C), suggesting further that type B does not function in vivo as a carbonic anhydrase. The versatility of the catalytic activity of carbonic anhydrase for a number of 'artificial' substrates suggested that enzyme B may be utilized in reactions of intermediary metabolism. A number of hydration, dehydration, decarboxylation, kinase, and phosphatase systems were tested to determine a possible physiological function for the enzyme. Results with eighteen possible substrates were negative and the possibility is discussed that mammalian carbonic anhydrase B is an evolutionary accident.
mesh_terms: D002256:Carbonic Anhydrases / Q000097:blood*; D003890:Desiccation; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000097:blood
chemical_list: D007527:Isoenzymes; D002256:Carbonic Anhydrases