The administration of 5-hydroxy-L-tryptophan to growing cells yielded a new blue pigment. The chemical structure was determined to be 5-(5-hydroxyindol-3-yl)-3-(5-hydroxy-3-oxoindolylidene)-4-pyrroline-2-one, mainly by using proton- and carbon 13-NMR. Feeding experiments of 5-hydroxytryptophan labeled with deuterium and carbon-13 unambiguously demonstrated that the hydroxylation of tryptophan was the first step for violacein biosynthesis. No incorporation of 5-hydroxy-[4, 6-2H2]tryptamine suggests that decarboxylation of 5-hydroxy-L-tryptophan was not the second reaction, but should take place at a later stage in the pathway of violacein formation. 5-Hydroxy-[4, 6-2H2]indole was not incorporated, indicating that an enzyme like tryptophanase was unlikely to have been involved in violacein biosynthesis.
Japan Society for Bioscience, Biotechnology, and Agrochemistry