A possible role of d-valine and related d-amino acids in repression of enzyme and actinomycin synthesis

The addition of d-valine and related d-amino acids to the production medium blocks kynurenine formamidase II and actinomycin D synthesis by Streptomyces parvulus. This effect may be due to a direct inhibition of the actinomycin synthetase-catalyzed racemization of l-valine to its peptide bound d-form during antibiotic formation. In addition, the d-amino acid(s) may influence enzyme and actinomycin synthesis through carbon and/or nitrogen catabolite regulation. The relatively slow uptake and metabolism of the d-amino acid would provide a continuous supply of catabolite(s) that repress transcription of actinomycin biosynthetic genes over a long period of time.