Effect of structural and stereochemical methylproline isomers on actinomycin biosynthesis

The inhibitory effect of methylprolines on actinomycin biosynthesis by Streptomyces antibioticus was studied; the order of effectiveness was 3- >4- >5-methyl-dl-proline. Cis-3-methyl-dl-proline was 14 times more active than the trans isomer. It was also found that 4- and, possibly, 5-methylproline were incorporated into the actinomycin molecule. When 4-methylproline was present, three new actinomycins, representing 50 to 60% of the antibiotic mixture, were synthesized. Growth of the organism may be stimulated at concentrations (0.1 to 1.0 mug per ml) of 3-methylproline that inhibit antibiotic formation, thus providing additional evidence for a different mechanism of actinomycin synthesis from that of protein synthesis. Azetidine-2-carboxylic acid, piperdine-2-carboxylic acid, and hydroxyproline (but not sarcosine) reversed the inhibition due to 3-methylproline.

Influence of isoleucine upon quinomycin biosynthesis by Streptomyces sp. 732

When dl-isoleucine was added to an ammonium nitrate-maltose medium during cultivation of Streptomyces sp. 732, quinomycin B formation was selectively enhanced (from 3 to 70% of the quinomycin mixture) and quinomycin C synthesis was inhibited completely. In addition, two new quinomycins, designated quinomycins D and E, were produced in the presence of isoleucine. These compounds were found to contain N-methylalloisoleucine. In experiments with isoleucine enantiomorphs, it was determined that the order of effectiveness for quinomycin B synthesis was dl-isoleucine > d-isoleucine > l-isoleucine. The extent to which quinomycin B synthesis is enhanced depends upon the concentration and the time of addition of isoleucine to the medium. The effect of dl-isoleucine was reduced to some extent by the addition of l-valine. It is conceivable that amino acids which are precursors of the N-methylamino acids in quinomycin can regulate quinomycin formation.

Ciguatoxin: isolation and chemical nature

Ciguatoxin, the agent responsible for ciguatera, a disease produced in humans from ingestion of certain fishes, has been isolated from specimens of the moray eel, Gymnothorax javanicus. The toxin is apparently a lipid containing quaternary nitrogen, hydroxyl, and carbonyl functions.