CARBONIC-ANHYDRASES IN HIGHER-PLANTS AND AQUATIC MICROORGANISMS

At physiological pH-values CO2 and HCO3- are the dominant inorganic ca rbon species and the interconversion between both is catalyzed by carb onic anhydrase (EC 4.2.1.1). This enzyme is widely distributed among p hotosynthetic organisms. In the first part of the review, the similari ties and the differences of carbonic anhydrases from plants and animal s are briefly described. In the second part recent advances in molecul ar biology to understand the structure of carbonic anhydrase from high er terrestrial plants as well as its involvement in photosynthetic CO2 fixation are summarized. Lastly, the review deals with the presence o f carbonic anhydrase in aquatic organisms including cyanobacteria, mic roalgae, macroalgae and angiosperms. Evidence for the presence of extr acellular and intracellular isozymes in these organisms are discussed. The properties and function(s) of carbonic anhydrase during the opera tion of the inorganic carbon concentrating mechanism are also describe d.