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Purification and characterization of mannitol dehydrogenase from Aspergillus parasiticus
Abstract:
Mannitol dehydrogenase, NADP specific (EC 1.1.1.138), was purified from mycelium of Aspergillus parasiticus (1-11-105 Whl). The enzyme had a molecular weight of 1.4 X 10(5) and was composed of four subunits of apparently equal size. The substrate specificity was limited to D-mannitol, D-glucitol, D-arabinitol, 1-deoxy-D-mannitol, and 1-deoxy-D-glucitol. Zinc ion was a powerful inhibitor of the enzyme, inhibition being competitive with respect to mannitol, with Ki and 1 microM. It is proposed that the stimulation of polyketide synthesis by zinc ion may be mediated in part by inhibition of mannitol dehydrogenase.
Insights
Mannitol dehydrogenase from Aspergillus parasiticus was purified and characterized. Zinc ions were found to inhibit this enzyme, suggesting a role in regulating polyketide synthesis.
Area of Science:
- Biochemistry
- Enzymology
- Mycology
Background:
- Mannitol dehydrogenase (EC 1.1.1.138) is an enzyme involved in carbohydrate metabolism.
- Aspergillus parasiticus is a fungus known for producing mycotoxins, including polyketides.
Purpose of the Study:
- To purify and characterize mannitol dehydrogenase from Aspergillus parasiticus.
- To investigate the effect of zinc ions on mannitol dehydrogenase activity and its potential role in polyketide synthesis.
Main Methods:
- Enzyme purification from Aspergillus parasiticus mycelium.
- Determination of molecular weight and subunit composition.
- Enzyme kinetics and substrate specificity assays.
- Inhibition studies using zinc ions.
Main Results:
- Purified mannitol dehydrogenase with a molecular weight of 1.4 x 10(5) Da, composed of four equal subunits.
- Enzyme exhibited specificity for D-mannitol and related sugar alcohols.
- Zinc ion competitively inhibited the enzyme with a Ki of 1 microM.
Conclusions:
- The characterization of Aspergillus parasiticus mannitol dehydrogenase provides insights into fungal metabolic pathways.
- Zinc ion-mediated inhibition of mannitol dehydrogenase is proposed as a mechanism influencing polyketide synthesis in this organism.