Experimental evidence of d-glutamate racemase activity in the uncultivated bacterium Candidatus Saccharimonas aalborgensis.

Autor: Peñalver M; Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.; Department of Molecular Biology, Universidad Autónoma de Madrid (UAM), Madrid, Spain.; Centro de Biologia Molecular Severo Ochoa (CBM), CSIC-UAM, Madrid, Spain., Paradela A; Proteomics Facility, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain., Palacios-Cuéllar C; Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain., Pucciarelli MG; Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.; Department of Molecular Biology, Universidad Autónoma de Madrid (UAM), Madrid, Spain.; Centro de Biologia Molecular Severo Ochoa (CBM), CSIC-UAM, Madrid, Spain., García-Del Portillo F; Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.
Jazyk: angličtina
Zdroj: Environmental microbiology [Environ Microbiol] 2024 Apr; Vol. 26 (4), pp. e16621.
DOI: 10.1111/1462-2920.16621
Abstrakt: The Candidate Phyla Radiation (CPR) encompasses widespread uncultivated bacteria with reduced genomes and limited metabolic capacities. Most CPR bacteria lack the minimal set of enzymes required for peptidoglycan (PG) synthesis, leaving it unclear how these bacteria produce this essential envelope component. In this study, we analysed the distribution of d-amino acid racemases that produce the universal PG components d-glutamate (d-Glu) or d-alanine (d-Ala). We also examined moonlighting enzymes that synthesize d-Glu or d-Ala. Unlike other phyla in the domain Bacteria, CPR bacteria do not exhibit these moonlighting activities and have, at most, one gene encoding either a Glu or Ala racemase. One of these 'orphan' racemases is a predicted Glu racemase (MurI CPR ) from the CPR bacterium Candidatus Saccharimonas aalborgenesis. The expression of MurI CPR restores the growth of a Salmonella d-Glu auxotroph lacking its endogenous racemase and results in the substitution of l-Ala by serine as the first residue in a fraction of the PG stem peptides. In vitro, MurI CPR exclusively racemizes Glu as a substrate. Therefore, Ca. Saccharimonas aalborgensis may couple Glu racemization to serine and d-Glu incorporation into the stem peptide. Our findings provide the first insights into the synthesis of PG by an uncultivated environmental bacterium and illustrate how to experimentally test enzymatic activities from CPR bacteria related to PG metabolism.
(© 2024 The Authors. Environmental Microbiology published by John Wiley & Sons Ltd.)
Databáze: MEDLINE
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