Dietary excess of leucine affects tryptophan–niacin metabolism adversely and has thus been implicated in the etiology of pellagra. To understand the biochemical basis of leucine-induced changes in tryptophan–niacin metabolism the effect of leucine on enzymes of tryptophan–niacin metabolism was investigated. Excess of leucine in the diet had no effect on rat liver 3-hydroxyanthranilate oxygenase and nicotinate phosphoribosyltransferase but significantly decreased the activity of quinolinate phosphoribosyltransferase of rat liver and kidney. The activities of tryptophan oxygenase in liver and picolinate carboxylase in kidney were significantly higher in leucine-fed animals than in the controls. Also, oxidation of [U-14C]tryptophan in vivo was higher in leucine-fed animals. Increased picolinate carboxylase and decreased quinolinate phosphoribosyltransferase activities would result in a decrease in NAD formation from dietary tryptophan. Lowered NAD formation from tryptophan particularly when the niacin concentrations in the diet are marginal would result in a state of conditioned niacin deficiency.
Skip Nav Destination
Research Article| June 01 1973
Effect of leucine on enzymes of the tryptophan–niacin metabolic pathway in rat liver and kidney
Biochem J (1973) 134 (2): 425–430.
- Views Icon Views
- Share Icon Share
Ghafoorunissa, B. S. Narasinga Rao; Effect of leucine on enzymes of the tryptophan–niacin metabolic pathway in rat liver and kidney. Biochem J 1 June 1973; 134 (2): 425–430. doi: https://doi.org/10.1042/bj1340425
Download citation file:
Don't already have an account? Register
Get Access To This Article
Buy This Article