Work

NagX, a periplasmic β- N -acetylglucosaminidase, contributes to NagZ-independent β-lactamase expression in Stenotrophomonas maltophilia

Year: 2026

Type: article

Abstract: ABSTRACT Beta-lactam resistance in Stenotrophomonas maltophilia is primarily mediated by the expression of L1 and L2 β-lactamases. L1/L2 expression is closely linked to peptidoglycan recycling through the AmpNG-NagZ-AmpR pathway, in which NagZ plays a dominant role for L1/L2 expression. Although a NagZ-independent β-lactamase expression has been suggested, its molecular basis remains unclear. Here, we identify NagX, a periplasmic β- N -acetylglucosaminidase, as a key contributor to the NagZ-independent β-lactamase pathway. Using S. maltophilia KJ and its derived nagZ in-frame deletion mutant, KJΔNagZ, we confirm the presence of NagZ-independent β-lactamase expression and an additional β- N -acetylglucosaminidase in addition to NagZ. Determination of β-lactamase and β- N -acetylglucosaminidase activities in various engineered strains of S. maltophilia KJ demonstrated that NagX is a periplasmic β- N -acetylglucosaminidase and drives NagZ-independent β-lactamase expression in an AmpNG- and AmpR-dependent manner. To reveal how NagX processes the released peptidoglycan sacculus, the periplasmic muropeptides profile of wild-type KJ, KJΔAmpNG (an ampNG mutant), and KJΔAmpNGΔNagX (an ampNG and nagX double mutant) were determined by LC-MS/MS. The results demonstrated that NagX can remove the N -acetylglucosamine (GlcNAc) moiety from the GlcNAc-anhMurNAc-peptide and GlcNAc-anhMurNAc, yielding anhMurNAc-peptide and anhMurNAc, respectively. AmpNG permease system shuttled GlcNAc-anhMurNAc-peptide, GlcNAc-anhMurNAc, and anhMurNAc-peptide from periplasm to cytosol. Then, the anhMurNAc-peptide served as activator ligands that cooperate with AmpR to induce β-lactamase expression. Our findings uncover a novel NagX-AmpNG-AmpR circuit underlying NagZ-independent β-lactamase expression in S. maltophilia .

Source: Antimicrobial Agents and Chemotherapy

DOI: 10.1128/aac.00243-26

Authors: En-Wei Hu, Po-Cheng Kuo, Li-Hua Li, Chen-Syuan Yen, Cheng-Chih Hsu, Tsuey-Ching Yang

Institutions: National Yang Ming Chiao Tung University, National Taiwan University, Taipei Veterans General Hospital, Taipei Medical University

Language: English

Topic: Infections and bacterial resistance

Subfield: Endocrinology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Good health and well-being

Open Access status: diamond

Funders: National Science and Technology Council, Shanghai Educational Development Foundation, National Science and Technology Council