Metabolites and enzyme activities involved in tryptophan metabolism in two different strains of mouse

The urinary excretion of the tryptophan metabolites along the kynurenine pathway and the variations of enzyme activities involved in the degradation of tryptophan have been studied in two strains of mice. The total excretion of the metabolites was significantly higher in the strain of albino N.C.L. than in Swiss albino mice, in accordance with the higher activity of tryptophan pyrrolase, which was present only as holoenzyme. In both strains kynurenine, kynurenic and xanthurenic acids were excreted in larger amounts. However, the albino N.C.L. mice excreted a large amount of xanthurenic acid, not correlated with the slightly higher kynurenine aminotransferase activity observed in this strain. The very high excretion of this metabolite indicates that the load of tryptophan causes a B6-deficiency. Liver kynureninase activity was similar in both strains. Correlation between total urinary excretion of the tryptophan metabolites and enzyme activities appears in the same strain of mice, even though differences are present in different strains.