The nitrate reductase activity of milk xanthine oxidase

Milk xanthine oxidase oxidizes xanthine at pH 9.6 and reduces nitrates at pH 5.2. It is shown that the nitrate reductase activity requires molybdenum and sulfur-containing sites in the enzyme, whereas oxidation of xanthine also requires iron-containing sites and FAD. As the pH changes from 5.2 to 9....

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Bibliographic Details
Published inJournal of applied biochemistry Vol. 7; no. 2; p. 86
Main Authors Sergeev, N S, Ananiadi, L I, L'vov, N P, Kretovich, W L
Format Journal Article
LanguageEnglish
Published United States 01.04.1985
Subjects
Animals
Calcium Chloride - pharmacology
Cattle
Chloromercuribenzoates - pharmacology
Dithioerythritol - pharmacology
Flavin-Adenine Dinucleotide - metabolism
Hot Temperature
Hydrogen-Ion Concentration
Milk - enzymology
Nitrate Reductases - metabolism
p-Chloromercuribenzoic Acid
Protein Conformation
Xanthine Oxidase - metabolism
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Summary:Milk xanthine oxidase oxidizes xanthine at pH 9.6 and reduces nitrates at pH 5.2. It is shown that the nitrate reductase activity requires molybdenum and sulfur-containing sites in the enzyme, whereas oxidation of xanthine also requires iron-containing sites and FAD. As the pH changes from 5.2 to 9.6, the conformation of the enzyme molecule is modified as demonstrated by changes in the absorption, fluorescence, and circular dichroism spectra. When the enzyme is treated with dithioerythritol, it may pass from the oxidase to the dehydrogenase form with a marked increase in the nitrate reductase activity.
ISSN:0161-7354