Biodegradation pathway of l-glutamatediacetate by Rhizobium radiobacter strain BG-1

An aerobic bacterium was isolated from activated sludge in a medium containing l-glutamate-N,N-diacetate (l-GLDA) as sole carbon and energy source. The isolate was identified as a Rhizobium radiobacter species. Besides l-GLDA, the strain utilized nitrilotriacetate (NTA) and proposed intermediates in l-GLDA metabolism such as glyoxylate and l-glutamate. l-GLDA-grown cells oxidized l-GLDA, l-glutamate but not iminodiacetate (IDA), and trans-ketoglutaconate, indicating removal of a carboxymethyl group as an initial degradation reaction. The removal of the first carboxymethyl group of l-GLDA is catalyzed by an NADH-dependent mono-oxygenase. The oxidative deamination of l-glutamate by a dehydrogenase resulting in the formation of oxoglutarate was also detected in cell-free extracts of R. radiobacter sp. A pathway for the metabolism of l-GLDA R. radiobacter sp. is proposed: First, l-GLDA leads to l-glutamate-N-monoacetate (l-GLMA) which in turn leads to l-glutamate. Then, l-glutamate leads to oxoglutarate, an intermediate of the TCA cycle.