| Abstract: | The possible role of some metabolic systems producing acetyl-CoA, and methylmalonyl-CoA as initial precursors in the biosynthesis of the macrolide antibiotic A 6599 by Streptomyces hygroscopicus JA 6599 was studied. The activities of pyruvate decarboxylase exceeded in two higher producing strains about twofold those found in the mycelium of a lower producing one suggesting that in this organism an enhanced production of acetyl-CoA should be one of the prerequisites necessary for an improved antibiotic biosynthesis. No clear interrelationship was established, however, between the biosynthesis of the secondary metabolite A 6599 on the one hand and the acetate and propionate kinase content on the other hand. In S. hygroscopicus JA 6599 the carboxylation of acetyl-CoA or propionyl-CoA seems to be the major pathway giving malonyl-CoA or methylmalonyl-CoA, respectively. Thus, the activities of acetyl-CoA and propionyl-CoA carboxylases corresponded with both the levels of antibiotic production in several strains and with variations observed in the specific antibiotic production rate during the cultivation. Some other pathways synthesizing these precursors, e.g. via oxaloacetate, are assumed to be negligible since even in the mycelium of the lower producing strain increased activities of phosphoenolpyruvate carboxylase were present. |
