TY - JOUR
T1 - Ultrasensitive behavior in the synthesis of storage polysaccharides in cyanobacteria
AU - Gómez-Casati, Diego F.
AU - Cortassa, Sonia
AU - Aon, Miguel A.
AU - Iglesias, Alberto A.
N1 - Funding Information:
Acknowledgements This work was supported by grants from Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina; PIP 0443/98) and Agencia Nacional de Promoción Científica y Tecnológica (PICT’99 No. 1-6074). The authors thank J.L. Burgos for technical assistance. D.F.G.-C. is a fellow from CONICET; M.A.A., S.C., and A.A.I. are researchers from the same institution.
PY - 2003/4/1
Y1 - 2003/4/1
N2 - The glycogen synthetic pathway operates ultrasensitively as a function of the ADPglucose pyrophosphorylase (ADPGlcPPase) allosteric effectors, 3-phosphoglycerate and Pi, in permeabilized cells of the cyanobacterium Anabaena PCC 7120. In vitro data previously showed that the ultrasensitive behavior of ADPGlcPPase depends upon cross-talk between the two allosteric effectors, the enzyme's response being additionally modulated by molecular crowding [D.F. Gómez Casatiet al. (2000) Biochem J 350:139-147]. In the present work we show, experimentally and with a mathematical model, that α-1,4-glucan synthesis is also ultrasensitive in cells due to the propagation of the switch-like behavior of ADPGlcPPase to the synthetic pathway. Amplifications of up to 20-fold in storage-polysaccharide synthesis can be achieved with a modest 6.7-fold increase in 3-phosphoglycerate in the presence of 5 mM Pi in contrast to the 30-fold necessary in its absence. This is the first time that this phenomenon has been reported to occur in the glycogen synthetic pathway of a photosynthetic prokaryote. The implications of the results for plant cell physiology during light-dark transitions are discussed.
AB - The glycogen synthetic pathway operates ultrasensitively as a function of the ADPglucose pyrophosphorylase (ADPGlcPPase) allosteric effectors, 3-phosphoglycerate and Pi, in permeabilized cells of the cyanobacterium Anabaena PCC 7120. In vitro data previously showed that the ultrasensitive behavior of ADPGlcPPase depends upon cross-talk between the two allosteric effectors, the enzyme's response being additionally modulated by molecular crowding [D.F. Gómez Casatiet al. (2000) Biochem J 350:139-147]. In the present work we show, experimentally and with a mathematical model, that α-1,4-glucan synthesis is also ultrasensitive in cells due to the propagation of the switch-like behavior of ADPGlcPPase to the synthetic pathway. Amplifications of up to 20-fold in storage-polysaccharide synthesis can be achieved with a modest 6.7-fold increase in 3-phosphoglycerate in the presence of 5 mM Pi in contrast to the 30-fold necessary in its absence. This is the first time that this phenomenon has been reported to occur in the glycogen synthetic pathway of a photosynthetic prokaryote. The implications of the results for plant cell physiology during light-dark transitions are discussed.
KW - ADPglucose pyrophosphorylase
KW - Anabaena
KW - Glycogen/starch synthesis
KW - Molecular crowding
KW - Permeabilized cyanobacteria
KW - Ultrasensitivity (of enzymes)
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U2 - 10.1007/s00425-002-0949-4
DO - 10.1007/s00425-002-0949-4
M3 - Article
C2 - 12687364
AN - SCOPUS:0037832406
SN - 0032-0935
VL - 216
SP - 969
EP - 975
JO - Planta
JF - Planta
IS - 6
ER -