tph, tryptophan hydroxylase; trp, tryptophan biosynthesis; kynU, kynureninase; prsA, ribose-phosphate pyrophosphokinase; gua, purine biosynthesis; add, adenosine deaminase; udk, uridine kinase; pyrE, UMP synthase; upp, uracil phosphororibosyl transferase. * Asterisk indicates remnants.