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On the mechanism of action of xanthine oxidase. Evidence in support of an oxo transfer mechanism in the molybdenum-containing hydroxylases.

Authors
  • Hille, R
  • Sprecher, H
Type
Published Article
Journal
The Journal of biological chemistry
Publication Date
Aug 15, 1987
Volume
262
Issue
23
Pages
10914–10917
Identifiers
PMID: 3611096
Source
Medline
License
Unknown

Abstract

The mechanism of action of xanthine oxidase has been investigated using single-turnover experiments in an effort to determine the primary source of the oxygen atom incorporated into product in the course of catalysis. It is found from mass spectroscopic analysis of the uric acid generated in these experiments that when 16O-labeled enzyme in [18O]H2O is reacted with substoichiometric amounts of xanthine (under conditions where no enzyme molecule is likely to react with more than one substrate molecule), the uric acid isolated from the reaction mixture contains 16O at position 8 of the purine ring. Conversely, when 18O-labeled enzyme in [16O]H2O is exposed to substoichiometric xanthine, 18O is incorporated into the product uric acid. These results strongly support a variety of chemical studies with model molybdenum complexes suggesting that the oxygen atom of the Mo = O group known to be present at the active site of xanthine oxidase is transferred to product in the course of catalysis. The mechanistic implications of the present work are discussed.

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