Enterococcus faecalis is a Gram-positive clinical pathogen causing severe
infections. Its survival during
infection depends on its ability to utilize host-derived metabolites, such as
protein-deglycosylation products. We have identified in E. faecalis OG1RF a locus (ega) involved in the catabolism of the glycoamino
acid N-acetylglucosamine-
L-asparagine. This locus is separated into two transcription units, genes egaRP and egaGBCD1D2, respectively. RT-qPCR experiments revealed that the expression of the ega locus is regulated by the transcriptional repressor EgaR. Electromobility shift assays evidenced that
N-acetylglucosamine-
L-asparagine interacts directly with the EgaR
protein, which leads to the transcription of the ega genes. Growth studies with egaG, egaB and egaC mutants confirmed that the encoded
proteins are necessary for
N-acetylglucosamine-
L-asparagine catabolism. This glycoamino
acid is transported and phosphorylated by a specific
phosphotransferase system EIIABC components (OG1RF_10751, EgaB, EgaC) and subsequently hydrolyzed by the
glycosylasparaginase EgaG, which generates
aspartate and 6-P-N-acetyl-β-d-glucosaminylamine. The latter can be used as a fermentable
carbon source by E. faecalis. Moreover, Galleria mellonella larvae had a significantly higher survival rate when infected with ega mutants compared to the wild-type strain, suggesting that the loss of
N-acetylglucosamine-
L-asparagine utilization affects enterococcal virulence.