Role of external carbonic anhydrase in light-dependent alkalization byFucus serratus L. andLaminaria saccharina (L.) Lamour. (Phaeophyta) |
| |
Authors: | Kurt Haglund Ziyadin Ramazanov Matern Mtolera Marianne Pedersén |
| |
Affiliation: | (1) Department of Physiological Botany, Uppsala University, P.O. Box 540, S-751 21 Uppsala, Sweden;(2) Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, -276 Moscow, Russia;(3) Institute of Marine Sciences, University of Dar es Salaam, P.O. Box 668, Zanzibar, Tanzania;(4) Present address: Department of Botany, Louisiana State University, 70803 Baton Rouge, LA, USA |
| |
Abstract: | It has been proposed that many marine macroalgae are able to utilize HCO3–for photosynthesis and growth, and that energy-dependent ion pumping is involved in this process. We have therefore studied the light-dependent alkalization of the surrounding medium by two species of marine macroscopic brown algae,Fucus serratus L. andLaminaria saccharina (L.) Lamour. with the aim of investigating the role of extracellular carbonic anhydrase (EC 4.2.1.1.) in the assimilation of inorganic carbon from the seawater medium. In particular, the influence of membrane-impermeable or slowly permeable carbonic-anhydrase inhibitors on the rate of alkalization of the seawater has been investigated. Inhibition of the alkalization rate occurred in both species at an alkaline pH (pH 8.0) but no inhibition was observed at an acidic pH (pH 6.0). The alkalization was found to be light-dependent and inhibited by 3-(3 ,4 -dichlorophenyl)-1, 1-dimethylurea and, thus, correlated with photosynthesis. Alkalization by macroalgae has previously been shown to be proportional to inorganiccarbon uptake. We suggest that alkalization of the medium at alkaline pH in both of the species examined is mainly the consequence of an extracellular reaction. The reaction is catalyzed by extracellular carbonic anhydrase which converts HCO3–to OH– and CO2; CO2 is then taken up through the plasmalemma. However, we do not exclude the involvement of other mechanisms of inorganic-carbon uptake.Abbreviations AZ acetazolamide - CA carbonic anhydrase - CAext extracellular carbonic anhydrase - Ci inorganic carbon - DBS dextran-bound sulfonamide - DCMU 3-(3 ,4 -dichloro-phenyl)-1,1-dimethylurea - PPFD photosynthetic photon flux densityThis study was carried out with financial support by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Carl Trygger's Fund for Scientific Research (Sweden), SJFR (Swedish Council for Forestry and Agricultural Research) and CICYT (Spain). Z. Ramazanov is an invited professor of Ministerio de Educación y Ciencia, Spain. |
| |
Keywords: | Alkalization Carbon assimilation Carbonic anhydrase Fucus Laminaria Macroalgae Photosynthesis |
本文献已被 SpringerLink 等数据库收录! |
|