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Studies on sucrose-phosphate synthase from rice leaves
G L Salerno1, G C Pagnussat, H G Pontis
1Centro de Investigaciones Biológicas, Fundación para Investigaciones Biológicas Aplicadas and PROBIOP-CONICET, Mar del Plata, Argentina.
Cellular and Molecular Biology (Noisy-Le-Grand, France)
|June 10, 1998
Summary
Two forms of sucrose-phosphate synthase (SPS) were purified from rice leaves, exhibiting distinct biochemical properties and regulatory responses. These findings offer insights into sucrose metabolism regulation in plants.
Area of Science:
- Biochemistry
- Plant Physiology
Background:
- Sucrose-phosphate synthase (SPS) is a key enzyme in sucrose biosynthesis.
- Understanding SPS biochemical properties is crucial for elucidating carbon flux regulation in plants.
Purpose of the Study:
- To characterize the biochemical properties and peptide composition of SPS in rice seedlings.
- To investigate the differences between distinct SPS enzyme forms.
Main Methods:
- Enzyme purification using DEAE-Sephacel chromatography, gel filtration (Sepharose 6B), and anion exchange chromatography (Mono Q).
- Enzyme activity assays and kinetic analysis (Km values for Fru-6P and UDP-Glc).
- Analysis of effector modulation (Glc-6-P and Pi) and molecular mass determination.
Main Results:
- Two SPS forms (SPS-I and SPS-II) were separated, with SPS-II showing higher purification and specific activity.
- SPS-I exhibited a significantly higher Km for UDP-Glc and was unaffected by Glc-6-P and Pi, unlike SPS-II.
- A native molecular mass of approximately 420 kDa was determined, and a 116 kDa polypeptide was detected in rice leaves but not roots.
Conclusions:
- Rice leaf seedlings contain at least two distinct SPS forms with differential kinetic and regulatory properties.
- These findings highlight the complex regulation of sucrose synthesis in rice.
- SPS expression is localized to rice leaves, suggesting tissue-specific roles.