Abstract
Activities of some special flavin enzymes of rat liver which have been found to be markedly depressed in riboflavin deficiency were measured when the animals were divided into 4 groups fed on diets containing 0,7,25 and 40% of protein respectively. Xanthine oxidase activity was scarcely detected in the liver of rats fed on the protein free diet. The maximal activity was observed in the case of the 25% protein diet. Activities of glycolic acid oxidase, D-amino acid oxidase and glycine oxidase remained to some extent in the liver of rats fed on the protein free diet and gave their maximum values in the case of the 7% protein diet. The greater part of xanthine oxidase was present in the supernatant fraction of cells, while the other enzymes were distributed in both of mitochondrial and supernatant fractions. In comparison of these results with those obtained in riboflavin deficiency, it was observed that activities of three enzymes, except xanthine oxidase might be depend on the riboflavin content of the tissue, but xanthine oxidase activity was affected not only by riboflavin content but by the amounts of protein uptake. Discussions were made on the behaviour of these flavin enzymes and the metabolisms of substrates in the liver.
