Cysteinyl-tRNA Synthetase from Astragalus Species
1School of Environmental and Life Sciences, Murdoch University, Murdoch, 6153, Western Australia.
Plant Physiology
|June 1, 1979
Summary
This study purified cysteinyl-tRNA synthetases from Astragalus plants. Most species efficiently used selenocysteine, but A. bisulcatus showed unique substrate specificity, failing to utilize selenocysteine.
Area of Science:
- Biochemistry
- Plant Science
- Enzymology
Background:
- Cysteinyl-tRNA synthetases (EC 6.1.1.16) are crucial enzymes in protein synthesis.
- Some Astragalus species accumulate selenium, suggesting unique metabolic pathways.
Purpose of the Study:
- To investigate the substrate specificities of cysteinyl-tRNA synthetases in selenium-accumulating and non-accumulating Astragalus species.
- To compare the kinetic properties of these enzymes with different amino acid substrates.
Main Methods:
- Partial purification of l-Cysteinyl-tRNA synthetases from four Astragalus species and Phaseolus aureus.
- Enzyme assays to determine substrate specificities and kinetic parameters (K(m) values) for cysteine, selenocysteine, and alpha-aminobutyric acid.
Main Results:
- All tested species, except A. bisulcatus, exhibited similar K(m) values for cysteine, selenocysteine, and alpha-aminobutyric acid.
- A. bisulcatus failed to use selenocysteine as a substrate and displayed a fourfold higher K(m) for cysteine compared to other species.
Conclusions:
- The study reveals distinct substrate specificities in cysteinyl-tRNA synthetases among Astragalus species, particularly highlighting A. bisulcatus's unique biochemical profile.
- These findings contribute to understanding selenium metabolism and enzyme adaptation in plants.
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