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Published on: July 3, 2011
Isomaltulose is actively metabolized in plant cells
1University of Queensland, Brisbane, Queensland 4072, Australia.
Plant Physiology
|October 20, 2011
Summary
Isomaltulose is not a nonmetabolized sugar in plants, as intracellular enzymes can break it down. This finding impacts plant physiology studies and biotechnology applications for enhanced sugar production.
Area of Science:
- Plant Physiology
- Biochemistry
- Biotechnology
Background:
- Isomaltulose, a sucrose isomer, is widely used in plant studies as a nonmetabolized sugar.
- Its use in human nutrition is increasing due to beneficial properties like a low glycemic index.
- Previous understanding suggested plants lack pathways to metabolize isomaltulose.
Purpose of the Study:
- To investigate the catabolism of isomaltulose by intracellular plant enzymes.
- To re-evaluate the assumption of isomaltulose as a nonmetabolized sugar in physiological studies.
- To explore potential applications in plant biotechnology for sugar yield enhancement.
Main Methods:
- Studied sugarcane and other plant species.
- Assessed extracellular and intracellular metabolism of isomaltulose.
- Performed kinetic studies on soluble acid invertase (SAI) and sucrose synthase activity.
- Compared substrate specificities for sucrose and its isomers.
Main Results:
- Plants do not readily import or catabolize extracellular isomaltulose.
- Intracellular enzymes, particularly vacuolar soluble acid invertase (SAI) and cytosolic sucrose synthase, substantially catabolize isomaltulose.
- SAI exhibits lower specificity for isomaltulose compared to sucrose (10% of specificity constant).
- Enzyme activity varies significantly among different sucrose isomers and plant species.
Conclusions:
- The notion of isomaltulose and other sucrose isomers as nonmetabolized sugars in plants is inaccurate.
- Cell lysis can lead to significant hydrolysis of exogenous isomaltulose, affecting downstream signaling.
- Enzymatic properties of sucrose isomer metabolism can be leveraged for improved sugar yields in plant biotechnology.
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