Journal of Experimental Botany, Vol 49, 1917-1924, Copyright © 1998 by Oxford University Press
J Krook, D Vreugdenhil, C Dijkema and L van der Plas
Cells were grown in batch culture on a mixture of 50 mM glucose and
fructose as the carbon source; either the glucose or the fructose was
[1-13C]-labelled. In order to investigate the uptake
and conversion of glucose and fructose during long-term labelling
experiments in cell suspensions of Daucus carota L.,
samples were taken every 2 d during a 2 week culture period and sucrose and
starch were assayed by means of HPLC and 13C-nuclear
magnetic resonance. The fructose moieties of sucrose had a lower labelling
percentage than the glucose moieties. Oxidative pentose phosphate pathway
activity in the cytosol is suggested to be responsible for this loss of
label of especially C-1 carbons. A combination of oxidative pentose
phosphate pathway activity, a relatively high activity of pathway to
sucrose synthesis and a slow equilibration between glucose-6-phosphate and
fructose-6-phosphate could explain these results. Starch contained glucose
units with a much lower labelling percentage than glucose moieties of
sucrose: it was concluded that a second, plastid-localized, oxidative
pentose phosphate pathway was responsible for removal of C-1 carbons of the
glucosyl units used for synthesis of starch. Redistribution of label from
[1-13C]-hexoses to
[6-13C]-hexoses also occurred: 18-45% of the label
was found at the C-6 carbons. This is a consequence of cycling between
hexose phosphates and those phosphates in the cytosol catalysed by PFP. The
results indicate that independent (oxidative pentose phosphate pathway
mediated) sugar converting cycles exist in the cytosol and
plastid.Key words: Daucus carotaL., cell suspensions,
carbon-13 nuclear magnetic resonance, 13C-NMR,
carbohydrate cycling, oxidative pentose phosphate pathway, plastid.
ARTICLES
Sucrose and starch metabolism in carrot (Daucus carota L.) cell suspensions analysed by 13-labelling: indications for a cytosol and a plastid-localized oxidative pentose phosphate pathway
Department of Plant Physiology, Wageningen Agricultural University, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands; Department of Molecular Physics, Wageningen Agricultural University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands; Corresponding author e-mail: Jan.hendrikKrook@algem.pf.wau.nl
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  A. P. Alonso, H. Vigeolas, P. Raymond, D. Rolin, and M. Dieuaide-Noubhani A New Substrate Cycle in Plants. Evidence for a High Glucose-Phosphate-to-Glucose Turnover from in Vivo Steady-State and Pulse-Labeling Experiments with [13C]Glucose and [14C]Glucose Plant Physiology, August 1, 2005; 138(4): 2220 - 2232. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Sriram, D. B. Fulton, V. V. Iyer, J. M. Peterson, R. Zhou, M. E. Westgate, M. H. Spalding, and J. V. Shanks Quantification of Compartmented Metabolic Fluxes in Developing Soybean Embryos by Employing Biosynthetically Directed Fractional 13C Labeling, Two-Dimensional [13C, 1H] Nuclear Magnetic Resonance, and Comprehensive Isotopomer Balancing Plant Physiology, October 1, 2004; 136(2): 3043 - 3057. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. A. Running, R. P. Burlingame, and A. Berry The pathway of L-ascorbic acid biosynthesis in the colourless microalga Prototheca moriformis J. Exp. Bot., August 1, 2003; 54(389): 1841 - 1849. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Glawischnig, A. Gierl, A. Tomas, A. Bacher, and W. Eisenreich Starch Biosynthesis and Intermediary Metabolism in Maize Kernels. Quantitative Analysis of Metabolite Flux by Nuclear Magnetic Resonance Plant Physiology, December 1, 2002; 130(4): 1717 - 1727. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Rontein, M. Dieuaide-Noubhani, E. J. Dufourc, P. Raymond, and D. Rolin The Metabolic Architecture of Plant Cells. STABILITY OF CENTRAL METABOLISM AND FLEXIBILITY OF ANABOLIC PATHWAYS DURING THE GROWTH CYCLE OF TOMATO CELLS J. Biol. Chem., November 8, 2002; 277(46): 43948 - 43960. [Abstract] [Full Text] [PDF]
|
|