Metabolic pathway for the utilization of L-arginine, L-ornithine, agmatine, and putrescine as nitrogen sources in Escherichia coli K-12

Abstract

The pathway for the utilization of L-arginine, agmatine, L-ornithine, and putrescine as the sole nitrogen source by Escherichia coli K-12 has been elucidated. Mutants impaired in the utilization of one or more of the above compounds were isolated, and their growth on the different compounds as a sole source of nitrogen and the activities of enzymes of the putative pathway were examined. Our results show that L-arginine is first decarboxylated to agmatine, which is hydrolyzed to urea and putrescine. L-Ornithine is decarboxylated to putrescine. Putrescine is transaminated to γ-aminobutyraldehyde, which is oxidized to γ-aminobutyric acid. γ-Aminobutyric acid is degraded to succinate. The gene for putrescine aminotransferase was located at 89 min on the E. coli K-12 chromosome, and the gene for γ-aminobutyraldehyde (pyrroline) dehydrogenase was mapped at approximately 30 min.