Alterations of the tryptophan--nicotinic acid metabolism in vitiligo
De Antoni, A.; Cardin Dè Stefani, E.L.; Costa, C.; Vanzan, S.; Allegri, G.
Acta Vitaminologica et Enzymologica 4(3): 237-243
1982
ISSN/ISBN: 0300-8924 PMID: 7148608 Document Number: 196477
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.