Rhizobial enzyme reveals pH-driven catalytic switching and ʟ-amino acid incorporation by ʟ,-transpeptidases
- 1The University of Sheffield
Abstract
Nearly all bacteria are surrounded by a mesh-like macromolecule called peptidoglycan that gives them their shape and helps them resist turgor pressure. To grow and maintain their peptidoglycan, bacteria produce a wide range of enzymes, including the relatively understudied ,[x1D05]-transpeptidase (LDT) family. LDTs can catalyse several different reactions and vary widely in copy number: some bacteria have none, whilst others have more than twenty. To better understand why some bacteria have so many LDTs, we examined 18 putative ones from Rhizobium johnstonii, a nitrogen-fixing, symbiotic bacterium. Heterologous expression revealed several highly active enzymes, one of which, LdtRj8, we further characterized in detail. In vitro assays showed that LdtRj8 was capable of ,[x1D05]-transpeptidation, carboxypeptidation, substitution, and endopeptidation, but that its preferred activity differed at different pHs. LdtRj8 particularly excelled at ,[x1D05]-substitution, utilizing all of the tested [x1D05]-amino acids, and, surprisingly, most of the -amino acids as well. LdtRj8's pH-modulated activity could help R. johnstonii respond to acidic conditions encountered throughout the rhizobium-legume symbiosis, and its -amino acid substitution activity, which we show to be a more general property of LDTs, may regulate ,[x1D05]-transpeptidation and explain the existence of isomeric muropeptides often reported in the literature.
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BibTeX
@misc{rady2026rhizobial,
title = {{Rhizobial enzyme reveals pH-driven catalytic switching and ʟ-amino acid incorporation by ʟ,-transpeptidases}},
author = {B. J. Rady and R. Bahadur and C. A. Evans and S. Mesnage},
howpublished = {bioRxiv},
year = {2026},
month = jun,
doi = {10.64898/2026.06.30.735398},
url = {https://www.biorxiv.org/content/10.64898/2026.06.30.735398v2},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Rhizobial enzyme reveals pH-driven catalytic switching and ʟ-amino acid incorporation by ʟ,-transpeptidases
AU - B. J. Rady
AU - R. Bahadur
AU - C. A. Evans
AU - S. Mesnage
PY - 2026
DA - 2026/06/30
PB - bioRxiv
DO - 10.64898/2026.06.30.735398
UR - https://www.biorxiv.org/content/10.64898/2026.06.30.735398v2
AB - Nearly all bacteria are surrounded by a mesh-like macromolecule called peptidoglycan that gives them their shape and helps them resist turgor pressure. To grow and maintain their peptidoglycan, bacteria produce a wide range of enzymes, including the relatively understudied ,[x1D05]-transpeptidase (LDT) family. LDTs can catalyse several different reactions and vary widely in copy number: some bacteria have none, whilst others have more than twenty. To better understand why some bacteria have so many LDTs, we examined 18 putative ones from Rhizobium johnstonii, a nitrogen-fixing, symbiotic bacterium. Heterologous expression revealed several highly active enzymes, one of which, LdtRj8, we further characterized in detail. In vitro assays showed that LdtRj8 was capable of ,[x1D05]-transpeptidation, carboxypeptidation, substitution, and endopeptidation, but that its preferred activity differed at different pHs. LdtRj8 particularly excelled at ,[x1D05]-substitution, utilizing all of the tested [x1D05]-amino acids, and, surprisingly, most of the -amino acids as well. LdtRj8's pH-modulated activity could help R. johnstonii respond to acidic conditions encountered throughout the rhizobium-legume symbiosis, and its -amino acid substitution activity, which we show to be a more general property of LDTs, may regulate ,[x1D05]-transpeptidation and explain the existence of isomeric muropeptides often reported in the literature.
ER -