Diurnal and Seasonal Modulation of Sucrose Phosphate Synthase Activity in Leaves of Prosopis juliflora |
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Authors: | UV Pathre AK Sinha PA Shirke SA Ranade |
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Institution: | (1) National Botanical Research Institute, Lucknow, 226 001, India |
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Abstract: | Diurnal changes of sucrose-phosphate synthase (SPS) activity in different seasons were measured in Prosopis juliflora (Swartz) DC. leaves. SPS activity showed large variations with two distinct peaks, one around 09:00 and another at 21:00.
The diurnal pattern was apparently not due to circadian rhythm since the activities were directly related to the changes in
environmental parameters (irradiance, temperature, and leaf to air vapour pressure deficit) in different seasons. During the
day, the enzyme showed changes in kinetic properties, differential sensitivity to allosteric modulators, differential response
to ATP concentration, to concentration of endogenous sucrose, and to protein phosphatase inhibitors. These results taken together
indicate the modulation of SPS in synchrony with photosynthesis and suggest the existence of multiple levels of modulation,
presumably as an adaptive response to changing environmental extremes.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | allosteric modulation photosynthesis phosphorylation/dephosphorylation sucrose synthesis |
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