Origin of the sarcosine molecules of actinomycins

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Abstract
St_repfo-myces V-187 produces on minimal medium a mixture composed mainly of actinomycin C1 (actinomycin-D) and actinomycin-A1 (actinomycin-I). If sarcosine is added to the medium, the microorganism produces, in addition to actinomycins-C1 and A1, actinomycin-F1 (actinomycin-n) and actinomycin-F9 (actinomycin-(III), characterized by the substitution by sarcosine of one or both the proline molecules present in actino-mycin-C1. Exogenous sarcosine seems to be incorporated as such by Streptomyces V-187 only in the sarcosine molecule(s) that replace proline in the actinomycins of the F-group, whereas, for the synthesis of the other sarcosine molecules, the amino-acid is first demethylated to glycine. The incorporation of sarcosine and glycine into actinomycin by S. antibioticus appears to follow a similar pattern, except that a portion of the methyl group produced in the degradation of sarcosine is utilized as a source of the methyl groups of the antibiotic. This explains the previously reported lack of cross-dilution between glycine and sarcosine observed in the incorporation of these amino-acids into actinomycin.