Production, Isolation, and Properties of Azetomycins

Abstract

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 ofactinomycin 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-IHI 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 gramnegative organisms. The relative inhibitory affect against growth and ribonucleic acid synthesis in Bacillus subtilis was: actinomycin IV > azet-I > azet-Il > >> 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 ,ug/ml, deoxyribonucleic acid synthesis was stimulated by these actinomycins.

Effect of phosphate and amino acids on echinomycin biosynthesis by Streptomyces echinatus

“…732 (which normally produces quinomycins A, B, and C) with L-isoleucine suppressed the synthesis of quinomycin A, stimulated the synthesis of quinomycin B, and provoked the biosynthesis of two new quinomycins, D and E. Thus, with this organism one or both valines were replaced by isoleucine. Similar compositional changes have been reported as regards the biogenesis of the peptide antibiotic actinomycin by cultures supplemented with L-amino acids found in the peptide or analogs thereof (4,5,10,16). By contrast, our results indicate that since S. echinatus is indeed a monoproducer, it lacks the genetic endowment to synthesize octapeptide quinomycin congeners, such as substituting isoleucine for valine, but apparently can substitute quinaldic acid for quinoxaline-2-carboxylic acid.…”

“…By contrast, Streptomyces echinatus produces echinomycin exclusively (2,11); consequently, it may be a better paradigm for the study of quinoxaline antibiotic biogenesis than species that produce more than one congener. In addition, since the only variation among the quinomycin series lies in the Nmethyl amino acid residue, this organism might respond to directed biosynthesis; compare the success achieved with proline substitution in the actinomycin series (4,5,10).…”

Novel Actinomycins Formed by Biosynthetic Incorporation of cis - and trans -4-Methylproline

“…A similar effect was noted in the replacement by pipecolic acid (12,18), but not by azetidine-2-carboxylic acid (10). It was also observed that substitution of proline by cis-4-methylproline reduced potency more than in the case of the trans isomer, i.e., K,, > K,, and Ka > K2.…”

“…Similar observations were made with pipecolic acid and azetidine-2-carboxylic acid (17), and, more recently, various novel actinomycins containing the latter. proline analogues have been isolated and characterized (10,11,18). The present study was designed to furnish individual actinomycins containing cis-and trans-4-methylproline for characterization and for comparisons of their biological activities with that of actinomycin D. For this purpose, Streptomyces parvulus (Streptomyces parvullus) was used with a modified culture medium (37).…”

Glutamate-induced uptake of proline by Streptomyces antibioticus

“…Furthermore, in the presence of L-glutamic acid, maximal quantitative yields of actinomycins are achieved (12). In addition, the qualitative and quantitative natures of the products can be modified by supplementing cultures with analogs of proline, such as pipecolic acid (PA) (6,11) or azetidine-2-carboxylic acid (4,11). Under these conditions, new actinomycins are produced in which one or both proline residues in the antibiotic molecule are replaced by the analog (4,5).…”