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Selenium-containing xanthine dehydrogenase from Eubacterium barkeri
T Schräder1, A Rienhöfer, J R Andreesen
1Institut für Mikrobiologie, Martin-Luther-Universität Halle, Germany.
European Journal of Biochemistry
|September 22, 1999
Summary
Researchers purified xanthine dehydrogenase from Eubacterium barkeri, revealing its complex structure and cofactor requirements. This enzyme plays a key role in purine metabolism.
Area of Science:
- Biochemistry
- Enzymology
- Microbiology
Background:
- Eubacterium barkeri utilizes xanthine as a growth substrate.
- A specific dehydrogenase is induced during xanthine metabolism.
Purpose of the Study:
- To purify and characterize the xanthine-induced dehydrogenase from Eubacterium barkeri.
- To elucidate the enzyme's structure, cofactor composition, and catalytic activities.
Main Methods:
- Enzyme purification using a three-step scheme.
- Spectrophotometric assays for enzyme activity.
- Native gel electrophoresis and SDS-PAGE for molecular mass determination.
- Activity reconstitution and fluorescence measurements for cofactor identification.
Main Results:
- Xanthine dehydrogenase was purified 39-fold, exhibiting high specific activity.
- The native enzyme (530 kDa) is a dodecamer composed of three subunit types.
- Molybdopterin (dinucleotide type) was identified as the molybdenum cofactor.
- The enzyme contains iron, sulfur, molybdenum, tungsten, selenium, and FAD.
- Selenium is not covalently bound to the protein.
Conclusions:
- Eubacterium barkeri possesses a unique xanthine dehydrogenase with a complex subunit and cofactor composition.
- The enzyme's characterization provides insights into purine catabolism in this bacterium.
- Selenium's non-covalent association suggests a novel regulatory or functional role.