Hartnup's disease is associated with disturbed metabolism of

(C) Tryptophan # HARTNUP DISEASE:> This disorder is characterized by reduced intestinal absorption & renal reabsorption of neutral amino acids.> The defect involves an amino acid transporter on the brush border of the jejunum & the proximal tubule. Intestinal absorption of free amino acids is reduced, though the neutral amino acids can be absorbed when present in di- & tripeptides.> Degradation of unabsorbed tryptophan by intestinal bacteria produces indolic acids that are absorbed & subsequently excreled at high levels in the urine of these patients.> The disorder is inherited as an autosomal recessive trait with an estimated incidence of 1 in 24,000 live births. Linkage analysis suggests a locus on chromosome 5.