Influence of valine, isoleucine, and related compounds on actinomycin synthesis.

Streptomyces antibioticus synthesizes a mixture of actinomycins (I to V), each of which possesses 2 moles of n-valine per mole of antibiotic (1, 2) ; occasionally a sixth substance is produced in trace amounts. Streptomyces chrysomallus, on the other hand, forms a mixture consisting of actinomycins IV (containing 2 moles of n-valine), VI (containing 1 mole of n-valine and 1 mole of n-alloisoleucine), and VII (containing 2 moles of n-alloisoleutine) (3). During an investigation concerned with the biogenesis of n-amino acids by these organisms, it was observed that the addition of o-valine (4), n-isoleucine, or n-alloisoleucine to a chemically defined medium in which S. antibioticus was growing resulted in a marked inhibition of actinomycin formation. The parallel between these results and those obtained in studies of penicillin biosynthesis with n-valine and nn-isoleucine (5, 6) prompted a further investigation of this phenomenon.