3-Hydroxyanthranilate, from tryptophan degradation

It was furthermore reported (K20) that nicotinic acid-deficient animals would grow only if given tryptophan, thus suggesting the conversion of tryptophan to nicotinic acid. Not only is tryptophan converted to nicotinic acid but also kynurenine and 3-hydroxyanthranilic acid. The peculiar degradation of the latter to pyridine derivatives gave rise to many interesting investigations. 3-Hydroxyanthranilic acid is derived from 3-hydroxykynurenine, another important tryptophan metabolite, the his-... 

Degradation of L-tryptophan in most organisms proceeds via L-kynurenine, 3-hydroxy-L-kynurenine, 3-hydroxyanthranilic acid and quinolinic acid to acetyl Co A and CO2 (Fig. 244). Anthranilic acid formed as an intermediate may be recycled to L-tryptophan (see above). The ring of 3-hydroxyanthranilic acid is cleaved by a dioxygenase (C 2.5). The x-amino-/3-carboxymuconic acid-e-semialdehyde formed either undergoes a cis trans isomerization of the Zl -double bond and cyclization to quinolinic acid, a compound synthesized in microorganisms and plants from aspartic acid and D-glyceraldehyde-3-phosphate (D 16.2). On the other hand o -amino-/3-carboxymuconic acid-e-aldehyde may be de-carboxylated and is then the immediate precursor of NH3, acetic acid and COg. 

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