August 1, 1995
View Full PaperXanthine oxidase and xanthine dehydrogenase
Key Points
- This review aims to explore the biochemistry of xanthine oxidase and xanthine dehydrogenase, particularly their relationship and roles in metabolic processes.
- Analysis of enzyme kinetics and redox behavior.
- Examination of binding site for NAD+ in xanthine dehydrogenase.
- Discussion on molecular biology and structural models of xanthine oxidizing enzymes.
- The two enzymes are shown to represent alternate forms of the same gene product.
- Xanthine dehydrogenase has a substantially lower reduction potential compared to xanthine oxidase.
- Evidence suggests these enzymes can reversibly interconvert under certain conditions.
Abstract
Xanthine oxidase and xanthine dehydrogenase are enzymes involved in the metabolism of purines and pyrimidines in various organisms. Their relationship to one another has been the subject of considerable debate, primarily because of their proposed roles in ischemia/reperfusion damage in tissues. Differences in the kinetics and oxidation-reduction behavior of the two forms are accounted for by the presence in the dehydrogenase of a binding site for NAD+, as well as a substantially lower reduction potential for the flavin FADH./FADH2 couple of the dehydrogenase relative to the oxidase. This review presents recent advances of our understanding of the biochemistry and molecular biology of these systems, including a model for the overall morphology of xanthine oxidizing enzymes. The evidence that the two enzymes represent alternate forms of the same gene product, in some cases reversibly interconvertible between one another, is discussed.