A LINK BETWEEN PRIMARY AND SECONDARY METABOLISM - MALONYL-COA FORMATION IN STREPTOMYCES-AMBOFACIENS GROWING ON AMMONIUM-IONS OR VALINE

Growth of Streptomyces ambofaciens in the presence of valine led to a greater production of spiramycin and excretion of short-chain fatty ac ids compared with growth on ammonium ions as nitrogen source. We deter mined the activities of enzymes that lead to the formation of malonyl- CoA, a key intermediate in the biosynthesis of spiramycin. In valine-g rown cultures, the activities of acetyl-CoA carboxylase and pyruvate d ehydrogenase were increased during the antibiotic production phase. Du ring this idiophase, oxaloacetate dehydrogenase activity was much high er in cultures growing on ammonium compared with valine. Two pathways are proposed concerning the mode of malonyl-CoA formation: a route via oxaloacetate dehydrogenase following growth on ammonium, and a route via acetyl-CoA carboxylase after growth on valine.