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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
agricultural and biological sciences
Kinetic model of sucrose accumulation in maturing sugarcane culm tissue
Phytochemistry, Volume 68, No. 16-18, Year 2007
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Description
Biochemically, it is not completely understood why or how commercial varieties of sugarcane (Saccharum officinarum) are able to accumulate sucrose in high concentrations. Such concentrations are obtained despite the presence of sucrose synthesis/breakdown cycles (futile cycling) in the culm of the storage parenchyma. Given the complexity of the process, kinetic modelling may help to elucidate the factors governing sucrose accumulation or direct the design of experimental optimisation strategies. This paper describes the extension of an existing model of sucrose accumulation (Rohwer, J.M., Botha, F.C., 2001. Analysis of sucrose accumulation in the sugar cane culm on the basis of in vitro kinetic data. Biochem. J. 358, 437-445) to account for isoforms of sucrose synthase and fructokinase, carbon partitioning towards fibre formation, and the glycolytic enzymes phosphofructokinase (PFK), pyrophosphate-dependent PFK and aldolase. Moreover, by including data on the maximal activity of the enzymes as measured in different internodes, a growth model was constructed that describes the metabolic behaviour as sugarcane parenchymal tissue matures from internodes 3-10. While there was some discrepancy between modelled and experimentally determined steady-state sucrose concentrations in the cytoplasm, steady-state fluxes showed a better fit. The model supports a hypothesis of vacuolar sucrose accumulation against a concentration gradient. A detailed metabolic control analysis of sucrose synthase showed that each isoform has a unique control profile. Fructose uptake by the cell and sucrose uptake by the vacuole had a negative control on the futile cycling of sucrose and a positive control on sucrose accumulation, while the control profile for neutral invertase was reversed. When the activities of these three enzymes were changed from their reference values, the effects on futile cycling and sucrose accumulation were amplified. The model can be run online at the JWS Online database (http://jjj.biochem.sun.ac.za/database/uys). © 2007 Elsevier Ltd. All rights reserved.
Authors & Co-Authors
Uys, Lafras
South Africa, Stellenbosch
Stellenbosch University
Botha, F. C.
South Africa, Mount Edgecombe
South African Sugarcane Research Institute
South Africa, Stellenbosch
Stellenbosch University
Hofmeyr, J. H.S.
South Africa, Stellenbosch
Stellenbosch University
Rohwer, Johann M.
South Africa, Stellenbosch
Stellenbosch University
Statistics
Citations: 107
Authors: 4
Affiliations: 2
Identifiers
Doi:
10.1016/j.phytochem.2007.04.023
ISSN:
00319422
Research Areas
Environmental
Noncommunicable Diseases