Stimulation of leucomycin production by magnesium phosphate and its relevance to nitrogen catabolite regulation.

Addition of magnesium phosphate [Mg3(PO4)2 x 8H2O] to a complex medium or to an ammonium ion-containing, chemically defined medium stimulated leucomycin production by Streptomyces kitasatoensis. Ammonium ions in high concentrations inhibited leucomycin production, but their limitation by magnesium phosphate led to the high production of the antibiotic.

Bioconversion and biosynthesis of nanaomycins using cerulenin, a specific inhibitor of fatty acid and polyketide biosyntheses.

The biosynthetic relationship of the nanaomycins produced by Streptomyces rosa var. notoensis OS-3966 was studied by means of a bioconversion method using the antibiotic cerulenin, a specific inhibitor of fatty acid and polyketide biosyntheses. Nanaomycin D was considered to be the first component produced from the hypothetical intermediate "polyketide". It is proposed that the biosynthesis sequence for the nanaomycin is: nanaomycin D leads to nanaomycin A leads to nanaomycin E leads to nanaomycin B. Nanaomycin B can be converted to nanaomycin A by non-enzymatic dehydration; however, nanaomycin A is rapidly bioconverted to nanaomycin E, which is the major component synthesized by the nanaomycin-producing strain.

Isolation and properties of spiramycin I 3-hydroxyl acylase from Streptomyces and ambofaciens.

An enzyme preparation able to acylate the hydroxyl group at C-3 of the lactone ring of spiramycin was obtained from the spiramycin-producing strain, Streptomyces ambofaciens ISP-5053. The enzyme was purified about 33-fold from the crude extract by means of ammonium sulfate fractionation, diethylaminoethyl (DEAE) cellulose batchwise elution and DEAE cellulose column chromatography. The optimum pH for the enzyme activity was 8.5. The enzyme was activated by Ca2++, Mg2+, and Mn2+ in this order, but was inhibited by various SH reagents. Spiramycin I was the best substrate for the enzyme. The enzyme showed no preference between acetyl-CoA and propionyl-CoA.

Bioconversion and biosynthesis of 16-membered macrolide antibiotics. XIII. Regulation of spiramycin I 3-hydroxyl acylase formation by glucose, butyrate, and cerulenin.

The effects of glucose, butyrate, and cerulenin on the formation of spiramycin I 3-hydroxyl acylase were investigated by using the cell-free extract prepared from the spiramycin-producing strain of Streptomyces ambofaciens KA-1028. Glucose induced the formation of the acylase, and this induction was remarkably repressed by butyrate. Cerulenin, on the other hand, not only cancelled the repression by butyrate but also stimulated the formation of the acylase. The unsuccessful trapping of spiramycin I as an intermediate during the bioconversion from neospiramycin I to spiramycin III in the presence of cerulenin was due to the rapid acylation of spiramycin I caused by the acylase induced by cerulenin.

Inhibition of the biosynthesis of leucomycin, a macrolide antibiotic, by cerulenin.

Cerulenin, an inhibitor of fatty acid synthesis, specifically inhibits the biosynthesis of leucomycin, a 16-membered macrolide antibiotic, in both growing cells and resting cells of Streptomyces kitasatoensis. In growing cells, the production of leucomycin was inhibited as long as cerulenin remained in the culture. In resting cells, 50 percent inhibition was achieved with a cerulenin concentration of 1.5 microgram/ml. Cells in which leucomycin synthesis was inhibited for 9 h remained capable of leucomycin synthesis upon removal of the inhibitor. Cerulenin specifically inhibits the incorporation of [14C]acetate into leucomycin but does not affect total protein or RNA synthesis. The uptake of [14C]acetate was not inhibited under conditions which completely inhibited the incorporation of acetate into leucomycin. Since cerulenin is known to block the condensation of malonyl-CoA subunits in the formation of fatty acids, it can be concluded that the aglycone of leucomycin is synthesized via the polyketide pathway by condensation steps similar to those involved in fatty acid biosynthesis.

A new antibiotic,, asukamycin, produced by Streptomyces.

Asukamycin, a new antibiotic, has been isolated from the culture broth of a streptomycete designated as Streptomyces nodosus subsp. asukaensis. The antibiotic inhibits the growth of Gram-positive bacteria including Nocardia asteroides. The empirical formula of antibiotic asukamycin has been proposed as C29H22N2O9 (M.W. 542). An acute toxicity of the antibiotic in mice is LD50 48.5 mg/kg by intraperitoneal injection and it has no effect on mice when it was administered by 450 mg/kg per os.