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Pyruvate carboxylase in the yeast pyc mutant
1Department of Biochemistry, University of Adelaide, Australia.
Archives of Biochemistry and Biophysics
|October 1, 1987
Summary
Yeast mutant pyc previously suspected of pyruvate carboxylase deficiency shows identical enzyme levels and molecular weights to wild type. Immunocytochemistry confirmed exclusive cytosolic localization in both strains.
Area of Science:
- Biochemistry
- Yeast Genetics
- Enzymology
Background:
- A yeast mutant (pyc) was previously identified with impaired utilization of key carbon sources.
- This defect was hypothesized to stem from a deficiency in pyruvate carboxylase.
Purpose of the Study:
- To re-evaluate the biochemical basis of the pyc yeast mutant's carbon source utilization defect.
- To investigate the activity, molecular properties, and localization of pyruvate carboxylase in the mutant and wild-type yeast.
Main Methods:
- Enzyme activity assays were performed.
- Native and subunit molecular weights of pyruvate carboxylase were determined.
- Immunocytochemical labeling was employed to ascertain enzyme localization.
Main Results:
- Pyruvate carboxylase activity levels were found to be identical in the pyc mutant and wild-type yeast.
- The native and subunit molecular weights of pyruvate carboxylase were also identical between the mutant and wild type.
- Immunocytochemical analysis revealed that pyruvate carboxylase is exclusively localized in the cytosol in both yeast strains.
Conclusions:
- The pyc yeast mutant's inability to utilize certain carbon sources is not due to a deficiency in pyruvate carboxylase activity or altered enzyme properties.
- The findings suggest that the defect in the pyc mutant lies elsewhere, as pyruvate carboxylase is present and correctly localized.