Journal Article

Utilization and Transport of Glucose in <i>Olea Europaea</i> Cell Suspensions

Jorge Oliveira, Rui M. Tavares and Hernâni Gerós

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 12, pages 1510-1517
Published in print December 2002 | ISSN: 0032-0781
Published online December 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf179
Utilization and Transport of Glucose in Olea Europaea Cell Suspensions

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Cell suspensions of Olea europaea var. Galega Vulgar grown in batch culture with 0.5% (w/v) glucose were able to transport d-[14C]glucose according to Michaelis–Menten kinetics associated with a first-order kinetics. The monosaccharide carrier exhibited high affinity (Km ≈50 µM) and was able to transport d-glucose, d-fructose, d-galactose, d-xylose, 2-deoxy-d-glucose and 3-O-methyl-d-glucose, but not d-arabinose, d-mannitol or l-glucose. d-[14C]glucose uptake was associated with proton uptake, which also followed Michaelis–Menten kinetics. The transport of 3-O-methyl-d-glucose was accumulative (40-fold, at pH 5.0) and the protonophore carbonyl cyanide m-chlorophenylhydrazone strongly inhibited sugar accumulation. The results were consistent with the involvement of a monosaccharide: proton symporter with a stoichiometry of 1 : 1. When cells were grown with 3% (w/v) glucose, the uptake of d-[14C]glucose followed first-order kinetics and monosaccharide:proton symporter activity was not detected. The value obtained for the permeability coefficient of hexoses in O. europaea cells supported the hypothesis that the first-order kinetics observed in 0.5% and 3% sugar-grown cells was produced exclusively by passive diffusion of the sugar. The results indicate that in O. europaea cells sugar levels have a regulatory effect on sugar transport, because the activity for monosaccharide transport was repressed by high sugar concentrations.

Keywords: Keywords: Monosaccharide transporter — Olea europaea (cell suspensions) — Sugar repression — Sugar uptake.; Abbreviations: CCCP, carbonyl cyanide m-chlorophenylhydrazone; 3-O-MG, 3-O-methyl-d-glucose; TPP+, tetraphenylphosphonium.

Journal Article.  5674 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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