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Purification and characterization of glucose-6-phosphate dehydrogenase from Aspergillus parasiticus
Abstract:
Glucose-6-phosphate dehydrogenase (EC 1.1.1.49) was purified from mycelium of Aspergillus parasiticus (1-11-105 Whl). The enzyme had a molecular weight of 1.8 X 10(5) and was composed of four subunits of apparently equal size. The substrate was very strict, only glucose 6-phosphate and glucose being oxidized by NADP or thio-NADP. Zinc ion was a powerful inhibitor of the enzyme, inhibition being competitive with respect to glucose 6-phosphate, with Ki about 2.5 microM. Other divalent metal ions which also serve as inhibitors are nickel, cadmium, and cobalt. It is proposed that the stimulation of polyketide synthesis by zinc ion may be mediated in part by inhibition. of glucose-6-phosphate dehydrogenase.
Insights
Researchers purified glucose-6-phosphate dehydrogenase from Aspergillus parasiticus. Zinc ions were found to be potent inhibitors of this enzyme, potentially influencing polyketide synthesis.
Area of Science:
- Biochemistry
- Enzymology
- Mycology
Background:
- Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme in cellular metabolism.
- Aspergillus parasiticus is a fungus known for producing various secondary metabolites.
Purpose of the Study:
- To purify and characterize glucose-6-phosphate dehydrogenase from Aspergillus parasiticus.
- To investigate the effect of metal ions, particularly zinc, on enzyme activity.
Main Methods:
- Enzyme purification from Aspergillus parasiticus mycelium.
- Determination of molecular weight and subunit composition.
- Enzyme kinetics studies using glucose-6-phosphate and glucose as substrates.
- Investigation of inhibition by divalent metal ions, including zinc.
Main Results:
- Purified G6PD from A. parasiticus with a molecular weight of 1.8 x 10(5) Da, composed of four equal subunits.
- The enzyme exhibited strict substrate specificity, oxidizing only glucose-6-phosphate and glucose with NADP or thio-NADP.
- Zinc ion was identified as a potent competitive inhibitor with respect to glucose-6-phosphate (Ki ≈ 2.5 µM).
- Nickel, cadmium, and cobalt ions also demonstrated inhibitory effects.
Conclusions:
- The characterization of Aspergillus parasiticus G6PD provides insights into its enzymatic properties.
- Zinc ion inhibition of G6PD suggests a potential regulatory role in metabolic pathways.
- The findings propose that zinc-mediated inhibition of G6PD may partially regulate polyketide synthesis in this fungus.