Evidence that an internal carbonic anhydrase is present in 5% CO2-grown and air-grown Chlamydomonas

• Published in: Plant physiology (Bethesda) Vol. 84; no. 3; pp. 757 - 761
• Main Authors: Moroney, J.V, Togasaki, R.K, Husic, H.D, Tolbert, N.E
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.07.1987
• Subjects: ALGAE; ALGUE; Berries; Biological and medical sciences; CARBON DIOXIDE; CARBONATE DEHYDRATASE; CARBONATE DESHYDRATASE; CARBONATO DEHIDRATASA; Cell growth; Cell lines; CELLS; CELLULE; CELULAS; CHLAMYDOMONAS REINHARDTII; Chloroplasts; DIOXIDO DE CARBONO; DIOXYDE DE CARBONE; ENZYME INHIBITORS; Enzymes; FOTOSINTESIS; Fundamental and applied biological sciences. Psychology; INHIBIDORES DE ENZIMAS; INHIBITEUR D'ENZYME; Metabolism; Periplasm; PHOTOSYNTHESE; PHOTOSYNTHESIS; Photosynthesis, respiration. Anabolism, catabolism; Plant cells; Plant physiology and development; Plants; Regulation(control); Carbonic anhydrase; Enzyme; Algae; Chlorophycophyta; Photosynthesis; Carbon; Thallophyta
• ISSN: 0032-0889; 1532-2548

Inorganic carbon (Ci) uptake was measured in wild-type cells of Chlamydomonas reinhardtii, and in cia-3, a mutant strain of C. reinhardtii that cannot grow with air levels of CO2. Both air-grown cells, that have a CO2 concentrating system, and 5% CO2-grown cells that do not have this system, were used. When the external pH was 5.1 or 7.3, air-grown, wild-type cells accumulated inorganic carbon (Ci) and this accumulation was enhanced when the permeant carbonic anhydrase inhibitor, ethoxyzolamide, was added. When the external pH was 5.1, 5% CO2-grown cells also accumulated some Ci, although not as much as air-grown cells and this accumulation was stimulated by the addition of ethoxyzolamide. At the same time, ethoxyzolamide inhibited CO2 fixation by high CO2-grown, wild-type cells at both pH 5.1 and 7.3. These observations imply that 5% CO2-grown, wild-type cells, have a physiologically important internal carbonic anhydrase, although the major carbonic anhydrase located in the periplasmic space is only present in air-grown cells. Inorganic carbon uptake by cia-3 cells supported this conclusion. This mutant strain, which is thought to lack an internal carbonic anhydrase, was unaffected by ethoxyzolamide at pH 5.1. Other physiological characteristics of cia-3 resemble those of wild-type cells that have been treated with ethoxyzolamide. It is concluded that an internal carbonic anhydrase is under different regulatory control than the periplasmic carbonic anhydrase.