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Hexokinase activity alters sugar-nucleotide formation in maize root homogenates
1Departamento de Bioquímica Medica, Instituto de Ciências Biomédicas, Universidad Federal do Rio de Janeiro, RJ, Brazil. galina@bioqmed.ufrj.br
Phytochemistry
|February 3, 2000
Summary
Maize root hexokinases show different ADP sensitivities. Mitochondrial hexokinase acts as the primary energy sensor, regulating sugar utilization based on ADP levels.
Area of Science:
- Plant Physiology
- Biochemistry
- Molecular Biology
Background:
- Hexokinases (HXKs) are crucial enzymes in glucose metabolism.
- Two HXK isoforms with varying ADP sensitivity exist in maize roots.
- Understanding HXK regulation is key to comprehending glucose utilization.
Purpose of the Study:
- To characterize ADP-sensitive hexokinase activities in maize roots.
- To investigate the impact of ADP on glucose-6-phosphate and NDP-5'-sugar levels.
- To elucidate the role of different HXK isoforms in energy sensing.
Main Methods:
- Pulse-chase experiments using D-[U-14C]glucose.
- Analysis of radio-labeled sugars via paper chromatography.
- Enzyme inhibition assays using ADP and mannoheptulose.
Main Results:
- NDP-5'-sugar formation was inhibited by ADP in a dose-dependent manner.
- Mannoheptulose preferentially inhibited mitochondrial-bound HXK over cytosolic HXK.
- Mitochondrial HXK activity was found to be highly sensitive to ADP fluctuations.
Conclusions:
- NDP-5'-sugar synthesis is regulated by ADP levels in maize roots.
- Mitochondrial HXK plays a significant role in sensing cellular energy charge.
- Differential sensitivity of HXK isoforms to inhibitors provides insights into their functions.