title: L-gulonolactone oxidase activity and vitamin C status in riboflavin-deficient rats.
abstract: The effect of riboflavin deficiency on the activity of L-gulonolactone oxidase [L-gulono-gamma-lactone: oxygen 2-oxidoreductase, EC 1.1.3.8] and on vitamin C status was studied. A marked decrease in the specific activity of L-gulonolactone oxidase was observed in the liver microsomes isolated from riboflavin-deficient rats: the specific activity was approx. one-third of that in the microsomes isolated from control rats. The L-ascorbic acid content in the liver of the riboflavin-deficient rats was approx. one-half of that in the liver of the control rats. It seems that the rate of production of L-ascorbic acid in the riboflavin-deficient rats is limited by the decreased level of L-gulonolactone oxidase activity. Immunotitration using rabbit antiserum directed to L-gulonolactone oxidase revealed that a substantial amount of an inactive form of this enzyme is present in the liver microsomes of the riboflavin-deficient rats. L-Gulonolactone oxidase activity in the microsomes of these rats increased by approx. 35% upon addition of FAD, but it was slightly decreased by the addition of FMN or riboflavin. These results indicate that the liver microsomes of the riboflavin-deficient rats contain a protein which exhibits L-gulonolactone oxidase activity upon addition of Fad.
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D005486:Flavin Mononucleotide / Q000494:pharmacology; D005182:Flavin-Adenine Dinucleotide / Q000494:pharmacology; D050544:L-Gulonolactone Oxidase; D007783:Lactones / Q000276:immunology / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D051381:Rats; D012257:Riboflavin Deficiency / Q000378:metabolism*; D013401:Sugar Alcohol Dehydrogenases / Q000276:immunology / Q000378:metabolism*
chemical_list: D007783:Lactones; D005182:Flavin-Adenine Dinucleotide; D005486:Flavin Mononucleotide; D013401:Sugar Alcohol Dehydrogenases; D050544:L-Gulonolactone Oxidase; D001205:Ascorbic Acid