Actinomycin E und Actinomycin F, zwei neue biosynthetische Actinomycingemische

Streptomyces echinatus produces only echinomycin (quinomycin A), in contrast to other streptomycetes, which produce families of quinoxaline antibiotics differing in the amino acid composition of the oligopeptide (quinomycins A, B, Bo, C, D, and E) or the structure of the sulfur-containing cross bridge (triostins A, B, and C). Attempts were made to establish conditions for directed biosynthesis with S. echinatus. The lability of the peptide lactone to alkaline pH was obviated by using high levels of phosphate or HEPES [4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid] buffer in the production medium. Maintaining the pH below 7.5 resulted in an apparent stimulation of production. Amino acids which serve as structural components or as precursors of echinomycin were employed singly or in combination with nitrate in a chemically defined medium. Based on specific yield (micrograms of echinomycin per milligram of mycelia [dry weight]), D-and L-serine, D-alanine, L-valine, and L-phenylalanine produced equivalent yields of antibiotic which were approximately twofold greater than yields obtained with nitrate alone. In contrast, L-alanine, P-alanine, and L-threonine produced a threeto fourfold stimulation of production. Although the other amino acids diminished antibiotic production, L-isoleucine, which ostensibly was inhibitory to production, supported the accumulation of a quinoxaline antibiotic in which the crossbridge sulfur lacked a methyl group.The family of quinoxaline antibiotics embraces two structurally related series referred to as the triostins and the quinomycins. Both series are similar in composition, consisting of two quinoxaline-2-carboxylic acid moieties attached to a cyclic octapeptide which contains a sulfur cross-linkage. They are distinguished in that the triostins contain a disulfide cross bridge, whereas the quinomycins contain a thioacetal cross bridge (3). The circularity of the oligopeptide is maintained by lactone bonds between the hydroxyl group of D-serine and the carboxyl group of the N-methyl amino acid (Fig. 1).Echinomycin (quinomycin A) differs from other natural quinomycin congeners in that its oligopeptide contains 2 mol each of N-methyl-Lvaline, D-serine, L-alanine, and L-cysteine (the latter as N-methyl-L-cysteine and N-methyl-Smethyl cysteine) (11). The major difference among the other natural congeners resides in the N-methyl amino acid residue which can occur as mono-or dimethylated alloisoleucines (11,15,18) with or without N-methyl valine in the other half-molecule.

Section: Resultssupporting

confidence: 88%

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

Formica¹,

Waring²

1983

“…Directed biosynthesis of the actinomycins has also been achieved in a number of instances (10,12,13,17,30,31,35). It has frequently been observed that the exogenously supplied amino acid or amino acid analogue is modified biochemically, e.g., via methylation, racemization, hydroxylation, or oxidation in a manner analogous to the endogenously synthesized amino acid (13).…”

Section: Discussionmentioning

confidence: 99%

“…Schmidt-Kastner (30,31) first noted that new actinomycins (El and E2) were synthesized by Streptomyces chrysomallus when the organism was grown in the presence of DL-isoleucine. It was reported (30,31) that one or two residues of N-methylisoleucine replaced one or two residues of N-methylvaline, respectively, in the parent compound, actinomycin C3.…”

mentioning

confidence: 99%

“…It was reported (30,31) that one or two residues of N-methylisoleucine replaced one or two residues of N-methylvaline, respectively, in the parent compound, actinomycin C3. More recently, our laboratory demonstrated that S. antibioticus and S. chrysomallus both form actinomycin mixtures which contain appreciable amounts of D-isoleucine and N-methyl-Lalloisoleucine (rather than N-methyl-isoleucine) when synthesis occurs with an isoleucine stereoisomer (15,35).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Branched-Chain Amino Acid Substitutions in the Biosynthesis of the Antibiotic Actinomycin

Yajima

Mason

Katz

1975

Actinomycins normally contain N-methyl-L-valine and either D-valine, Dalloisoleucine or both amino acids in the molecule. During antibiotic formation in a medium supplemented with one of the four isoleucine stereoisomers, Streptomyces parvulus and S. chrysomallus form complex actinomycin mixtures (Cl, C2, C3, El, and E2-like compounds). Although chromatographic techniques suggested that single homogeneous components had been isolated, subsequent studies indicated that such chromatographic fractions probably consisted of multiple isomers of actinomycin. Amino acid analyses revealed the presence of N-methylvaline and/or N-methylalloisoleucine and, in addition, D-isoleucine, D-valine, and D-alloisoleucine were frequently found in a given fraction.Schmidt-Kastner (30, 31) first noted that new actinomycins (El and E2) were synthesized by Streptomyces chrysomallus when the organism was grown in the presence of DL-isoleucine. It was reported (30, 31) that one or two residues of N-methylisoleucine replaced one or two residues of N-methylvaline, respectively, in the parent compound, actinomycin C3. More recently, our laboratory demonstrated that S. antibioticus and S. chrysomallus both form actinomycin mixtures which contain appreciable amounts of D-isoleucine and N-methyl-Lalloisoleucine (rather than N-methyl-isoleucine) when synthesis occurs with an isoleucine stereoisomer (15,35). N-methyl-L-alloisoleucine and D-isoleucine substitute for N-methyl-Lvaline and either D-valine or D-alloisoleucine, respectively, in the antibiotic peptides. Individual biosynthetic actinomycins were not examined; therefore, we initiated studies to establish the branched-chain amino acid composition of the isoleucine-induced actinomycin components formed by S. chrysomallus and S. parvulus. MATERIALS AND METHODSOrganisms and conditions of cultivation. S. chrysomallus (ATCC 11523) and S. parvulus (ATCC 12434) were maintained on slants of glucose-yeast extract-malt extract agar medium (9). Incubation was for 3 to 5 days at 30 C until sporulation had occurred; slants were then kept at 4 C until further use.For production of actinomycin the organisms were

“…Previous investigations have demonstrated that synthesis of novel actinomycins as well as enhanced formation of minor components occurs during antibiotic production in the presence of one of the four stereoisomers of isoleucine (16,22,33,34). i-Isoleucine and N-methyl-L-alloisoleucine were identified as amino acid constituents of the isoleucine-induced antibiotics elaborated by various Streptomyces species (20,38,39).…”

mentioning

confidence: 99%

Biogenetic Origin of the d -Isoleucine and N -Methyl- l -Alloisoleucine Residues in the Actinomycins

Yajima

Mason

Katz

1976

Studies with 14 C-labeled isoleucine stereisomers have established that l -alloisoleucine, d -alloisoleucine, and d -isoleucine may function as precursors for the biogenesis of d -isoleucine and N -methyl- l -alloisoleucine residues in actinomycin. l -[ 14 C]isoleucine appears to be employed chiefly for d -alloisoleucine (and N -methylisoleucine [?] formation); however, its role in the biosynthesis of d -isoleucine and N -methylalloisoleucine remains unclear. The potential pathway of biosynthesis of d -isoleucine and N -methyl- l -isoleucine is discussed.