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Abstract
The biosynthesis by Streptomyces griseus of candicidin, an aromatic polyene macrolide antibiotic, was inhibited by l-tryptophan, l-phenylalanine and, to a lesser degree, by l-tyrosine. A mixture of the three aromatic amino acids inhibited candicidin biosynthesis to a greater extent than did each amino acid separately. l-Tryptophan strongly inhibited the incorporation of the labelled precursors propionate or 4-aminobenzoic acid into candicidin. Incorporation of propionate into candicidin was 50 % inhibited by 2·5 mm-tryptophan. Inhibition by tryptophan did not require protein synthesis as the same effect was observed in cells in which protein synthesis was prevented by chloramphenicol. The inhibitory effect of l-tryptophan was partially reversed by exogenous 4-aminobenzoic acid suggesting that this effect is exerted at the level of 4-aminobenzoic acid synthase.
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