This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Moroney, J. V. Articles by Tolbert, N. E. Search for Related Content PubMed PubMed Citation Articles by Moroney, J. V. Articles by Tolbert, N. E. Agricola Articles by Moroney, J. V. Articles by Tolbert, N. E.

Articles

Effect of Carbonic Anhydrase Inhibitors on Inorganic Carbon Accumulation by Chlamydomonas reinhardtii¹

Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824

Membrane-permeable and impermeable inhibitors of carbonic anhydrase have been used to assess the roles of extracellular and intracellular carbonic anhydrase on the inorganic carbon concentrating system in Chlamydomonas reinhardtii. Acetazolamide, ethoxzolamide, and a membrane-impermeable, dextran-bound sulfonamide were potent inhibitors of extracellular carbonic anhydrase measured with intact cells. At pH 5.1, where CO₂ is the predominant species of inorganic carbon, both acetazolamide and the dextran-bound sulfonamide had no effect on the concentration of CO₂ required for the half-maximal rate of photosynthetic O₂ evolution (K_0.5[CO₂]) or inorganic carbon accumulation. However, a more permeable inhibitor, ethoxzolamide, inhibited CO₂ fixation but increased the accumulation of inorganic carbon as compared with untreated cells. At pH 8, the K_0.5(CO₂) was increased from 0.6 micromolar to about 2 to 3 micromolar with both acetazolamide and the dextran-bound sulfonamide, but to a higher value of 60 micromolar with ethoxzolamide. These results are consistent with the hypothesis that CO₂ is the species of inorganic carbon which crosses the plasmalemma and that extracellular carbonic anhydrase is required to replenish CO₂ from HCO₃^– at high pH. These data also implicate a role for intracellular carbonic anhydrase in the inorganic carbon accumulating system, and indicate that both acetazolamide and the dextran-bound sulfonamide inhibit only the extracellular enzyme. It is suggested that HCO₃^– transport for internal accumulation might occur at the level of the chloroplast envelope.

This article has been cited by other articles:

				M. Lapointe, T. D.B. MacKenzie, and D. Morse An External {delta}-Carbonic Anhydrase in a Free-Living Marine Dinoflagellate May Circumvent Diffusion-Limited Carbon Acquisition Plant Physiology, July 1, 2008; 147(3): 1427 - 1436. [Abstract] [Full Text] [PDF]

				J. V. Moroney and R. A. Ynalvez Proposed Carbon Dioxide Concentrating Mechanism in Chlamydomonas reinhardtii Eukaryot. Cell, August 1, 2007; 6(8): 1251 - 1259. [Full Text] [PDF]

				Y. Wang and M. H. Spalding An inorganic carbon transport system responsible for acclimation specific to air levels of CO2 in Chlamydomonas reinhardtii PNAS, June 27, 2006; 103(26): 10110 - 10115. [Abstract] [Full Text] [PDF]

				M. Mitra, S. M. Lato, R. A. Ynalvez, Y. Xiao, and J. V. Moroney Identification of a New Chloroplast Carbonic Anhydrase in Chlamydomonas reinhardtii Plant Physiology, May 1, 2004; 135(1): 173 - 182. [Abstract] [Full Text] [PDF]

				W. Leggat, M. R. Badger, and D. Yellowlees Evidence for an Inorganic Carbon-Concentrating Mechanism in the Symbiotic Dinoflagellate Symbiodinium sp. Plant Physiology, December 1, 1999; 121(4): 1247 - 1255. [Abstract] [Full Text]

				K. Van and M. H. Spalding Periplasmic Carbonic Anhydrase Structural Gene (Cah1) Mutant in Chlamydomonas reinhardtii Plant Physiology, July 1, 1999; 120(3): 757 - 764. [Abstract] [Full Text]

				N. A. Nimer, C. Brownlee, and M. J. Merrett Extracellular Carbonic Anhydrase Facilitates Carbon Dioxide Availability for Photosynthesis in the Marine Dinoflagellate Prorocentrum micans Plant Physiology, May 1, 1999; 120(1): 105 - 112. [Abstract] [Full Text]

				J. V. Moroney and A. Somanchi How Do Algae Concentrate CO2 to Increase the Efficiency of Photosynthetic Carbon Fixation? Plant Physiology, January 1, 1999; 119(1): 9 - 16. [Full Text]

				G. Amoroso, D. Sültemeyer, C. Thyssen, and H. P. Fock Uptake of HCO3- and CO2 in Cells and Chloroplasts from the Microalgae Chlamydomonas reinhardtii and Dunaliella tertiolecta Plant Physiology, January 1, 1998; 116(1): 193 - 201. [Abstract] [Full Text]