Carbonic anhydrase is an ancient enzyme widespread in prokaryotes. Journal   Proceedings of the National Academy of Sciences of the United States of America. Citation   Proc Natl Acad Sci U S A. 96(26):15184-9 Publication date   1999 Dec 21 Authors   Smith KS Jakubzick C Whittam TS Ferry JG Investigators   Gregory Ferry Grant agencies   National Institute of Allergy and Infectious Diseases National Institute of General Medical Sciences Grants   NIAID AI/GM42391 NIGMS GM44661 MeSH headings   Archaea Bacteria Carbonic Anhydrases Evolution, Molecular Prokaryotic Cells MeSH qualifiers   enzymology genetics Abstract   Carbonic anhydrases catalyze the reversible hydration of CO(2) and are ubiquitous in highly evolved eukaryotes. The recent identification of a third class of carbonic anhydrase (gamma class) in a methanoarchaeon and our present finding that the beta class also extends into thermophilic species from the Archaea domain led us to initiate a systematic search for these enzymes in metabolically and phylogenetically diverse prokaryotes. Here we show that carbonic anhydrase is widespread in the Archaea and Bacteria domains, and is an ancient enzyme. The occurrence in chemolithoautotrophic species occupying deep branches of the universal phylogenetic tree suggests a role for this enzyme in the proposed autotrophic origin of life. The presence of the beta and gamma classes in metabolically diverse species spanning the Archaea and Bacteria domains demonstrates that carbonic anhydrases have a far more extensive and fundamental role in prokaryotic biology than previously recognized. Medline ID   20079628