Two Systems for Concentrating CO2 and Bicarbonate during Photosynthesis by Scenedesmus

Autor:	N E Tolbert, J Thielmann, H Senger, Arun Goyal
Rok vydání:	1990
Předmět:	Growth medium biology Physiology Bicarbonate Chlamydomonas Diaphragm pump Plant Science Photosynthesis biology.organism_classification chemistry.chemical_compound chemistry Biochemistry Total inorganic carbon Carbon dioxide Genetics Biophysics Scenedesmus Metabolism and Enzymology
Zdroj:	Plant Physiology. 92:622-629
ISSN:	1532-2548 0032-0889
Popis:	Scenedesmus cells grown on high CO(2), when adapted to air levels of CO(2) for 4 to 6 hours in the light, formed two concentrating processes for dissolved inorganic carbon: one for utilizing CO(2) from medium of pH 5 to 8 and one for bicarbonate accumulation from medium of pH 7 to 11. Similar results were obtained with assays by photosynthetic O(2) evolution or by accumulation of dissolved inorganic carbon inside the cells. The CO(2) pump with K(0.5) for O(2) evolution of less than 5 micromolar CO(2) was similar to that previously studied with other green algae such as Chlamydomonas and was accompanied by plasmalemma carbonic anhydrase formation. The HCO(3) (-) concentrating process between pH 8 to 10 lowered the K(0.5) (DIC) from 7300 micromolar HCO(3) (-) in high CO(2) grown Scenedesmus to 10 micromolar in air-adapted cells. The HCO(3) (-) pump was inhibited by vanadate (K(i) of 150 micromolar), as if it involved an ATPase linked HCO(3) (-) transporter. The CO(2) pump was formed on low CO(2) by high-CO(2) grown cells in growth medium within 4 to 6 hours in the light. The alkaline HCO(3) (-) pump was partially activated on low CO(2) within 2 hours in the light or after 8 hours in the dark. Full activation of the HCO(3) (-) pump at pH 9 had requirements similar to the activation of the CO(2) pump. Air-grown or air-adapted cells at pH 7.2 or 9 accumulated in one minute 1 to 2 millimolar inorganic carbon in the light or 0.44 millimolar in the dark from 150 micromolar in the media, whereas CO(2)-grown cells did not accumulate inorganic carbon. A general scheme for concentrating dissolved inorganic carbon by unicellular green algae utilizes a vanadate-sensitive transporter at the chloroplast envelope for the CO(2) pump and in some algae an additional vanadate-sensitive plasmalemma HCO(3) (-) transporter for a HCO(3) (-) pump.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::e1fbb50787a5f07c66993f9a2b092932 https://doi.org/10.1104/pp.92.3.622 Zobrazit plný text záznamu