STUDIES ON THE BIOSYNTHESIS OF VIOLACEIN .4. A NEW METABOLITE OF TRYPTOPHAN, CHROMOPYRROLIC ACID, PRODUCED BY CHROMOBACTERIUM-VIOLACEUM

In order to trap the biosynthetic intermediate of violacein, a number of mutants were prepared. A novel tryptophan metabolite was produced by the administration of tryptophan to washed whole cells of the mutant of Chromobacterium violaceum. The chemical structure was determined to be 3,4-di-(3-indolyl)-pyrrole 2,5-dicarboxylic acid on the bases of H-1 and C-13-NMR spectra, and MS data. This compound was named chromopyrrolic acid, and was also detected in the various metabolites produced by the parent strain, although the amount produced was somewhat smaller. The structure of chromopyrrolic acid was closely related to that of violacein and deoxyviolacein. The pyrrole dicarboxylic acid moiety of chromopyrrolic acid was biosynthesized by condensation reactions of the tryptophan side chains of two tryptophan molecules, as was found in the biosynthesis of violacein. However, the 1,2-shift of the indole ring that was found in the biosynthesis of violacein did not occur. To confirm whether or not chromopyrrolic acid was a biosynthetic intermediate, a feeding experiment with radiolabeled chromopyrrolic acid was carried out. The incorporation into violacein analogues failed, indicating that chromopyrrolic acid was produced independently of violacein biosynthesis.