title: Alterations of the tryptophan--nicotinic acid metabolism in vitiligo.
abstract: Tryptophan metabolism "via kynurenine" is altered in vitiligo: after a load of the amino acid the urinary excretion of 3-hydroxykynurenine and 3-hydroxyanthranilic acid is decreased, whereas that of xanthurenic acid and its 8-methyl ether is increased. The excretory values of the metabolites suggest a deficiency of the activity of kynurenine hydroxylase and kynunerinase, the enzymes involved in the metabolism of 3-hydroxykynurenine and 3-hydroxyanthranilic acid. The reduced excretion of 3-hydroxykynurenine, a tryptophan metabolite involved in melanin biosynthesis, may indicate a smaller utilization of tryptophan in the biogenesis of the melanins.
mesh_terms: D015095:3-Hydroxyanthranilic Acid / Q000652:urine; D000328:Adult; D005260:Female; D006801:Humans; D006867:Hydrolases / Q000652:urine; D007736:Kynurenic Acid / Q000031:analogs & derivatives / Q000652:urine; D007737:Kynurenine / Q000031:analogs & derivatives / Q000378:metabolism / Q000652:urine; D050601:Kynurenine 3-Monooxygenase; D008297:Male; D008543:Melanins / Q000096:biosynthesis; D006899:Mixed Function Oxygenases / Q000652:urine; D008954:Models, Biological; D009525:Niacin / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*; D014820:Vitiligo / Q000378:metabolism*; D014977:Xanthurenates / Q000652:urine
chemical_list: D008543:Melanins; D014977:Xanthurenates; D015095:3-Hydroxyanthranilic Acid; D009525:Niacin; C005045:3-hydroxykynurenine; C023664:xanthurenic acid 8-methyl ether; D007737:Kynurenine; C028330:xanthurenic acid; D014364:Tryptophan; D006899:Mixed Function Oxygenases; D050601:Kynurenine 3-Monooxygenase; D006867:Hydrolases; C021480:kynureninase; D007736:Kynurenic Acid