The isolation and structure of actinomycins II and III

First Y-type actinomycins from Streptomyces with divergent structure-activity relationships for antibacterial and cytotoxic properties

Streptomyces sp. strain Gö-GS12 was found to produce five novel actinomycins Y(1)-Y(5) (). Their amino acid pattern discloses them as members of a new family of this important class of antibiotics. Compounds differ from Z-type actinomycins in their beta-peptidolactone rings which here contain trans-4-hydroxyproline (Hyp) or 4-oxoproline (OPro) amino acids, and from the X-congeners by containing methylalanine (MeAla). Within the new Y-type actinomycins variations are not only in the rare chlorinated or hydroxylated threonine residue. Furthermore, the beta-ring can undergo rearrangement by a two-fold acyl shift (compounds and ) or show a unique additional ring closure with the chromophore (compound ), resulting in metabolites with yet unknown structural motifs, altered conformations and distinct bioactivities. The strongest bioactivity was found for the chlorine containing actinomycin Y(1) (), the most surprising for Y(5) () with cytotoxic and antibacterial effects losing their coherence, which has been observed for the first time here.

Role of valine and isoleucine as regulators of actinomycin peptide formation by Streptomyces chrysomallus

Katz, Edward (Rutgers, The State University, New Brunswick, N. J.), Clarence R. Waldron, and Mary Lou Meloni. Role of valine and isoleucine as regulators of actinomycin peptide formation by Streptomyces chrysomallus. J. Bacteriol. 82:600-608. 1961-d-Valine is an effective inhibitor of actinomycin synthesis by Streptomyces chrysomallus; l-valine stimulates actinomycin production and reverses the inhibition due to the d-enantiomorph. The incorporation of l-valine into the medium results, particularly, in a marked increase in actinomycin IV formation. In studies with various isoleucine isomers it was shown that l-isoleucine enhances actinomycin VII production; the principal effect of d-alloisoleucine and, especially, d-isoleucine, is to bring about synthesis of two new actinomycins which contain N-methylisoleucine. Both l- and d-threonine were observed to have an effect similar to that obtained with l-isoleucine. An interpretation of these findings has been discussed.

Production, isolation, and properties of azetomycins

Streptomyces antibioticus synthesizes five actinomycins that differ in the "proline site" of the molecule. When cultured in the presence of azetidine-2-carboxylic acid (AzC), antibiotic synthesis was stimulated 40 to 50%, synthesis of actinomycin IV was inhibited, and one or both prolines were replaced by AzC. AzC incorporation could not be reversed by concomitant supplementation with proline or sarcosine, and only pipecolic acid affected a minor reversal of AzC incorporation. AzC-containing actinomycins were isolated and designated azet-I and azet-II; a third unresolved component or mixture was called azet-III. The molar ratio of AzC to proline was: azet-I, 1:1; azet-II, 2:0. Azet-III was equivocal. These azetidine actinomycins (azetomycins) were found to be potently inhibitory to the growth of selected gram-positive but not as potent to the growth of gram-negative organisms. The relative inhibitory affect against growth and ribonucleic acid synthesis in Bacillus subtilis was: actinomycin IV =/> azet-I > azet-II >>> azet-III. Protein synthesis was affected similarly; however, kinetic studies with B. subtilis revealed that ribonucleic acid synthesis was inhibited rapidly followed by an inhibition of protein synthesis. At concentrations less than 1 mug/ml, deoxyribonucleic acid synthesis was stimulated by these actinomycins.