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Effect of dietary protein and iron on the fractional turnover rate of rat liver xanthine oxidase

Journal Article · · J. Nutr.; (United States)
OSTI ID:5394170
;
Rat liver xanthine oxidase activity is regulated in response to dietary protein and iron. To investigate whether the change in activity was mediated by a change in the rate of protein degradation, we measured the fractional turnover rate using the double-isotope technique with (/sup 3/H)- and (/sup 14/C)leucine and calculated the apparent half-life of xanthine oxidase in rats fed diets containing either 20 or 5% casein with either 35 or 5 mg iron/kg diet. Under control conditions, xanthine oxidase had an apparent half-life of 4.8 d and approximately 65% of the enzyme subunits were active. Rats fed diets with low dietary protein had lower xanthine oxidase activity, but the enzyme had a slower fractional turnover rate, resulting in an apparent half-life of 6.4 d, and only 15-20% of the enzyme was active. The apparent half-life of xanthine oxidase increased to 7.5 d in rats fed diets with low dietary iron, but dietary iron did not affect the specific activity of the enzyme or the percentage of active subunits. These results suggest that the loss of enzyme activity is not due to loss of enzyme protein by increased degradation, but rather to inactivation of the enzyme.
Research Organization:
Univ. of California, Berkeley
OSTI ID:
5394170
Journal Information:
J. Nutr.; (United States), Journal Name: J. Nutr.; (United States) Vol. 117:12; ISSN JONUA
Country of Publication:
United States
Language:
English

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Related Subjects

550501 -- Metabolism-- Tracer Techniques
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINO ACIDS
ANIMALS
BIOLOGICAL EFFECTS
BIOLOGICAL HALF-LIFE
BODY
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
DIET
DIGESTIVE SYSTEM
DOUBLE LABELLING
ELEMENTS
ENZYME ACTIVITY
ENZYMES
GLANDS
IRON
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LABELLING
LEUCINE
LIVER
MAMMALS
METABOLISM
METALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
OXIDOREDUCTASES
PROTEINS
RATS
RODENTS
TRACER TECHNIQUES
TRANSITION ELEMENTS
TRITIUM COMPOUNDS
VERTEBRATES