Studies of the biosynthesis of actinomycin in protoplasts from Streptomyces antibioticus.

Protoplasts actively synthesizing actinomycins have been prepared from Streptomyces, antibioticus. They showed an absolute requirement for the presence of oxygen, galactose, and alkaline earth ions. Sucrose was most efficient as an osmotic stabilizer. However, in air-saturated buffer the protoplasts seemed to be slightly inhibited in their metabolism. This is expressed by the appearance of 4-methyl-3-hydroxyanthranilic acid and the inability to utilize 1?¹⁴C]sarcosine for actinomycin synthesis. Evidence has been obtained that sarcosine and N-methyl-l-valine are not free precursors of the peptide-bound N-methyl-amino acids. It is further demonstrated that synthesis of actinomycin IV and actinomycin V differ from each other with respect to their different susceptibilities against the changings in the physiological environment of the protoplasts. Actinomycin synthesis is severely reduced when protoplasts are incubated in the presence of 10^?3, m methionine.