De Antoni A, Cardin Dè Stefani E L, Costa C, Vanzan S, Allegri G
Acta Vitaminol Enzymol. 1982;4(3):237-43.
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.
白癜风患者中，色氨酸通过犬尿氨酸途径的代谢发生改变：给予色氨酸负荷后，3-羟基犬尿氨酸和3-羟基邻氨基苯甲酸的尿排泄量减少，而黄尿酸及其8-甲醚的尿排泄量增加。这些代谢产物的排泄值表明犬尿氨酸羟化酶和犬尿氨酸酶活性不足，这两种酶参与3-羟基犬尿氨酸和3-羟基邻氨基苯甲酸的代谢。3-羟基犬尿氨酸是参与黑色素生物合成的色氨酸代谢产物，其排泄量减少可能表明黑色素生物合成中色氨酸的利用率降低。
