Kinetics and Thermodynamics of the Molecular Mechanism of the Reductive Half-Reaction of Xanthine Oxidase

The kinetics and thermodynamics of the reductive half-reaction of xanthine oxidase with xanthine as substrate have been investigated by stopped-flow kinetic measurements. The temperature dependence of the steady-state and transient kinetics of the reductive half-reaction reveals the existence of at...

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Bibliographic Details
Published in:Biochemistry (Easton) 1994-08, Vol.33 (34), p.10305-10312
Main Authors: Mondal, Madhu Sudan, Mitra, Samaresh
Format: Article
Language:English
Subjects:
Animals
Binding Sites
Cattle
Female
In Vitro Techniques
Kinetics
Milk - enzymology
Oxidation-Reduction
Substrate Specificity
Thermodynamics
Xanthine
Xanthine Oxidase - metabolism
Xanthines - chemistry
Xanthines - metabolism
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Summary:The kinetics and thermodynamics of the reductive half-reaction of xanthine oxidase with xanthine as substrate have been investigated by stopped-flow kinetic measurements. The temperature dependence of the steady-state and transient kinetics of the reductive half-reaction reveals the existence of at least three molecular intermediates during this half-reaction. All the microscopic rate constants and the thermodynamic activation parameters of the elementary steps of the reductive half-reaction have been determined for the first time. The microscopic rate constants and the thermodynamic activation parameters of the individual steps show wide variations in their magnitudes. The present work provides the most detailed and incisive description of the reaction of xanthine oxidase with its physiological substrate xanthine.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00200a010