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Characterization of NADP-dependent malic enzyme from developing castor oil seed endosperm
Heather L Shearer1, David H Turpin, David T Dennis
1Department of Biology, Queen's University, Kingston, Ont., Canada K7L 3N6. hshearer@uoguelph.ca
Archives of Biochemistry and Biophysics
|August 18, 2004
Summary
NADP-dependent malic enzyme (NADP-ME) in castor oilseeds provides carbon and NADPH for fatty acid synthesis. Its activity peaks during lipid accumulation, suggesting a key regulatory role in oilseed development.
Area of Science:
- Biochemistry
- Plant Physiology
- Molecular Biology
Background:
- Metabolic pathways in developing oilseed leucoplasts are crucial for fatty acid biosynthesis.
- NADP-dependent malic enzyme (NADP-ME) is a potential source of carbon and NADPH for this process in Ricinus communis.
Purpose of the Study:
- To investigate the role and regulation of NADP-ME in castor oilseed development.
- To characterize the kinetic and regulatory properties of castor NADP-ME.
Main Methods:
- Purification of NADP-ME from developing Ricinus communis endosperm.
- Determination of enzyme kinetics and effector responses.
- Analysis of enzyme activity during different stages of seed development.
Main Results:
- NADP-ME was purified 5160-fold with a specific activity of 18.2 U/mg.
- The enzyme is a homotetramer (254 kDa) with 63 kDa subunits.
- Acetyl-CoA and derivatives activated NADP-ME, indicating a regulatory function.
Conclusions:
- Castor NADP-ME plays a significant role in providing substrates for fatty acid biosynthesis.
- The enzyme's activity correlates with lipid accumulation, highlighting its importance in oilseed development.