Review Article

Immunomodulatory Effects Mediated by Serotonin

Figure 1

Metabolic pathways associated with 5-HT. The metabolic pathways branching from the catabolism of tryptophan are shown. Green and brown branches show kynurenine pathways from tryptophan. The dark blue branch displays the 5-HT generation pathway while the red branch displays the melatonin generation pathway (solid line) and the melatonin catabolism pathway (dashed lines). The 5-HT catabolism pathways are depicted in blue, purple, and cyan dotted lines. The most relevant compounds are circled with dotted lines and underlined compounds have no demonstrated effects. An additional catabolic pathway marked in pink from 5-hydroxy-L-tryptophan generates 5-hydroxy-kynurenine and 5-hidroxy-kynurenamine family compounds (paths C05648 and C05647), which have no demonstrated biological effects. The compounds in these pathways are denoted by their “Kyoto Encyclopedia of Genes and Genomes” (KEGG) code (http://www.genome.jp/kegg/). Enzymes with their classification codes (EC, http://www.chem.qmul.ac.uk/iubmb/enzyme/) and UNIPROT gene names are shown in squares. The shading arrows show the most studied pathways.