TDO2 and irritable bowel syndrome: In comparison to healthy individuals, IBS patients have been reported to have lower mucosal and higher systemic concentrations of 5-HT (5-hydroxytryptamine) and Kynurenic acid (KYNA). This was correlated with the association of the diverse microbiota found in IBS and the psychological disorders, which were evaluated with the Hospital Anxiety and Depression Scale and the Symptom Checklist-90. Escherichia coli, Achromobacter liquefaciens, and Paracolobacturm coliforme produces pyruvate by breaking down tryptophan into indole with the help of the enzyme tryptophanase.