Degradation of the microbial stress protectants and chemical chaperones ectoine and hydroxyectoine by a bacterial hydrolase\textendashdeacetylase complex
Abstract
When faced with increased osmolarity in the environment, many bacterial cells accumulate the compatible solute ectoine and its derivative 5-hydroxyectoine. Both compounds are not only potent osmostress protectants, but also serve as effective chemical chaperones stabilizing protein functionality. Ectoines are energy-rich nitrogen and carbon sources that have an ecological impact that shapes microbial communities. Although the biochemistry of ectoine and 5-hydroxyectoine biosynthesis is well understood, our understanding of their catabolism is only rudimentary. Here, we combined biochemical and structural approaches to unravel the core of ectoine and 5-hydroxy-ectoine catabolisms. We show that a conserved enzyme bimodule consisting of the EutD ectoine/5-hydroxyectoine hydrolase and the EutE deacetylase degrades both ectoines. We determined the high-resolution crystal structures of both enzymes, derived from the salt-tolerant bacteria Ruegeria pomeroyi and Halomonas elongata . These structures, either in their apo-forms or in forms capturing substrates or intermediates, provided detailed insights into the catalytic cores of the EutD and EutE enzymes. The combined biochemical and structural results indicate that the EutD homodimer opens the pyrimidine ring of ectoine through an unusual covalent intermediate, N -α-2 acetyl-l-2,4-diaminobutyrate (α-ADABA). We found that α-ADABA is then deacetylated by the zinc-dependent EutE monomer into diaminobutyric acid (DABA), which is further catabolized to l-aspartate. We observed that the EutD–EutE bimodule synthesizes exclusively the α-, but not the γ-isomers of ADABA or hydroxy–ADABA. Of note, α-ADABA is known to induce the MocR/GabR-type repressor EnuR, which controls the expression of many ectoine catabolic genes clusters. We conclude that hydroxy–α-ADABA might serve a similar function.
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BibTeX
@article{mais2026degradation,
title = {{Degradation of the microbial stress protectants and chemical chaperones ectoine and hydroxyectoine by a bacterial hydrolase\textendashdeacetylase complex}},
author = {Christopher-Nils Mais and Lucas Hermann and Florian Altegoer and Andreas Seubert and Alexandra A. Richter and Isa Wernersbach and Laura Czech and Erhard Bremer and Gert Bange},
journal = {Journal of Biological Chemistry},
year = {2026},
month = oct,
doi = {10.1074/jbc.ra120.012722},
url = {https://hal.science/hal-05780525v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Degradation of the microbial stress protectants and chemical chaperones ectoine and hydroxyectoine by a bacterial hydrolase\textendashdeacetylase complex
AU - Christopher-Nils Mais
AU - Lucas Hermann
AU - Florian Altegoer
AU - Andreas Seubert
AU - Alexandra A. Richter
AU - Isa Wernersbach
AU - Laura Czech
AU - Erhard Bremer
AU - Gert Bange
PY - 2026
DA - 2026/10/06
JO - Journal of Biological Chemistry
DO - 10.1074/jbc.ra120.012722
UR - https://hal.science/hal-05780525v1
AB - When faced with increased osmolarity in the environment, many bacterial cells accumulate the compatible solute ectoine and its derivative 5-hydroxyectoine. Both compounds are not only potent osmostress protectants, but also serve as effective chemical chaperones stabilizing protein functionality. Ectoines are energy-rich nitrogen and carbon sources that have an ecological impact that shapes microbial communities. Although the biochemistry of ectoine and 5-hydroxyectoine biosynthesis is well understood, our understanding of their catabolism is only rudimentary. Here, we combined biochemical and structural approaches to unravel the core of ectoine and 5-hydroxy-ectoine catabolisms. We show that a conserved enzyme bimodule consisting of the EutD ectoine/5-hydroxyectoine hydrolase and the EutE deacetylase degrades both ectoines. We determined the high-resolution crystal structures of both enzymes, derived from the salt-tolerant bacteria Ruegeria pomeroyi and Halomonas elongata . These structures, either in their apo-forms or in forms capturing substrates or intermediates, provided detailed insights into the catalytic cores of the EutD and EutE enzymes. The combined biochemical and structural results indicate that the EutD homodimer opens the pyrimidine ring of ectoine through an unusual covalent intermediate, N -α-2 acetyl-l-2,4-diaminobutyrate (α-ADABA). We found that α-ADABA is then deacetylated by the zinc-dependent EutE monomer into diaminobutyric acid (DABA), which is further catabolized to l-aspartate. We observed that the EutD–EutE bimodule synthesizes exclusively the α-, but not the γ-isomers of ADABA or hydroxy–ADABA. Of note, α-ADABA is known to induce the MocR/GabR-type repressor EnuR, which controls the expression of many ectoine catabolic genes clusters. We conclude that hydroxy–α-ADABA might serve a similar function.
SN - 0021-9258
SN - 1083-351X
ER -