Anthranilic acid and indole

Anthranilic acid and indole are precursors of tryptophan in numerous microorganisms and fungi (e.g., 5, 263, 264, 602, 741, 783, 785, 816, 854, 855, 876), and it is probable that anthranilic acid is derived, with intermediate steps, from the common precursor, CP of diagram 1. The conversion of anthranilic acid to indole and tryptophan has been shown unambiguously in Neurospora with the use of isotopic techniques (93, 663). There may, however, be other pathways for tryptophan biosynthesis (45, 702). Tryptophan can, for example, be formed by transamination of indolepyruvic acid (e.g., 470, 912), which might be formed other than via anthranilic acid. Thus aromatic-requiring mutants have been found which accumulate unidentified indole compounds (307). 

Tryptophan Biosynthesis. Tryptophan is another of the amino acids required by animals but synthesized only by plants and microorganisms. The synthesis of tryptophan in microorganisms has been outlined in recent years, but some of the reactions are still quite obscure. The known intermediates include shikimic acid, anthranilic acid, and indole. The mechanism of the conversion of shikimic acid to anthranilic acid has not been elucidated. 

When we come to tryptophan, which lies after shikimic acid, anthranilic acid and indole are found to be intermediates in the synthesis. The condensation of indole with serine to give tryptophan is brought about by the action of a specific enzyme, indole-ligase or tiyptophan desmolase, whose coenzyme is pytidoxal phosphate (this enzyme is not to be confused with tryptophanase which splits tryptophan into indole and pyrwoic acid). 

Early studies of the biosynthesis of L-tryptophan (3) established that both anthranilic acid and indole were able to replace L-tryptophan as a growth factor for some bacteria. The suggestion that these compounds were normal precursors of the aromatic amino acid was confirmed by Tatum, Bonner and Beadle " who showed that some L-tryptophan requiring mutants of Neurospora sp. responded to anthranilic acid or indole whilst others responded only to indole and accumulated anthranilic acid. Somewhat later other mutants were found which were blocked between indole and L-tryptophan and accumulated indole in the culture medium. 

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See also in sourсe #XX -- [ ]

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