Ammonium-assimilating enzymes and erythromycin formation in saccharolypospora erythrea

Abstract

Ammonium assimilation in Saccharolypospora erythrea was mediated by the glutamine synthetase/glutamate synthase pathway depending on the NH4 concentration in the culture medium. Glutamine synthetase formation was repressed by high ammonium concentration, and a rapid loss of its activity occurred after ammonium addition. There was difference in erythromycin biosynthesis and glutamine synthetase levels when L-glutamate of L-glutamine was added as the nitrogen source. When glutamic acid was used as the nitrogen source, the glutamine synthetase activity was high and there was no erythromycin production. But when glutamine was added, the glutamine synthetase level was low and the yield of the antibiotic was high. Glutamate synthase was formed independently of the nitrogen sources used, but glutamate dehydrogenase was present when ammonium was added as a nitrogen source, and it was NADH-dependent. There were high levels of alanine dehydrogenase in cultures grown with glycine, NH4C1, alanine and glutamine. Alanine most effectively induced the enzyme formation. The results suggest that there was no correlation between the levels of nitrogen-assimilating enzymes and erythromycin biosynthesis in this microorganism. © 1989, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.