抄録
The effect of dietary protein on pyrimidine-metabolizing enzymes was studied in the rat. The activities of dihydropyrimidine dehydrogenase and β-ureidopropionase in the livers of rats fed a protein-free diet were significantly decreased, while the activity of dihydropyrim-idinase was unaffected. Protein deficiency (5%) also decreased the activity of β-ureidopropionase. On the other hand, a high-protein diet (60%) increased the level of β-ureidopropionase. The activities of β-alanine-oxoglutarate aminotransferase (aminobutyrate aminotransferase) and D-3-aminoisobutyrate-pyruvate aminotransferase ((R )-3-amino-2-methylpropionate-pyruvate aminotransferase), which are present in mi-tochondria, depended on the amount of protein in the diet. Ammonium ions supplemented in the diet and given by injection did not affect the activities of rat liver pyrimidine-metabolizing enzymes (dihydropyrimi-dine dehydrogenase, dihydropyrimidinase, β-ureidopropionase, β-alanine-oxoglutarate aminotransferase and D-3-aminoisobutyrate-pyruvate ami-notransferase). Dietary uridine resulted in the accumulation of uracil in the liver, but did not affect the activities of pyrimidine-metabolizing enzymes.
