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.