FIGURE 4.

Tryptophan and its metabolites in sputum and the association with Pseudomonas aeruginosa. a) Tryptophan metabolism in Pseudomonas aeruginosa. There was a strong association between tryptophan and kynurenine and between kynurenine and kynurenic acid concentration in sputum. There was no association between kynurenine and 3-hydroxykynurenine concentration in sputum. This suggests that reaction 2 predominated over reaction 3 in the lungs of CF patients. b) Tryptophan, kynurenine and kynurenic acid are associated with relative abundance of Pseudomonas aeruginosa in sputum, but 3-hydroxykynurenine is not. FOR: formamidase; IDO: indoleamine-2,3-dioxygenase; KAT 1–IV: kynurenine aminotransferase; KYNU: kynureninase; TDO: tryptophan-2,3-dioxygenase.