MurNAc 6-phosphate etherase route of muramic acid recycling

A bacterial route that converts N-acetylmuramic acid (MurNAc) recovered from cell-wall turnover, or taken up from the environment, into N-acetylglucosamine 6-phosphate (GlcNAc-6P). MurNAc 6-phosphate (MurNAc-6P) is formed either by a MurNAc-specific phosphotransferase-system (PTS) transporter that phosphorylates MurNAc during uptake, or by the anhydro-MurNAc kinase AnmK acting on 1,6-anhydro-MurNAc released from imported anhydromuropeptides. The etherase MurQ then removes the D-lactyl ether from MurNAc-6P, yielding GlcNAc-6P and D-lactate, and GlcNAc-6P joins the GlcNAc catabolic pathway. The RpiR-family repressor MurR keeps the murP-murQ genes off until MurNAc-6P binds it. This catabolic etherase route is the alternative to the Pseudomonas-type anabolic MupP-AmgK-MurU shortcut (MODULE:peptidoglycan_recycling). Anhydromuropeptide import and the NagZ and AmpD steps that free anhydro-MurNAc are modeled in that module; GlcNAc-6P deacetylation and further catabolism are outside the boundary.

MODULE:murnac_6p_catabolic_recyclingDRAFTCONCRETEMetabolic Pathwaymodules/murnac_6p_catabolic_recycling.yaml
N-acetylmuramic acid catabolic processGO:0097173 1,6-anhydro-N-acetyl-beta-muramic acid catabolic processGO:0097175 peptidoglycan turnoverGO:0009254
GO:0097173
N-acetylmuramic acid catabolic process
Defines the biological-process boundary for MurNAc breakdown.
GO:0097175
1,6-anhydro-N-acetyl-beta-muramic acid catabolic process
Defines the recycling branch that starts from anhydro-MurNAc.
PMID:15060041
Identification of a phosphotransferase system of Escherichia coli required for growth on N-acetylmuramic acid.
Establishes MurP as the MurNAc-specific PTS EIIBC that depends on EIIA-Glc, and places MurNAc catabolism upstream of the GlcNAc pathway.
the catabolic pathway for MurNAc merges into the GlcNAc pathway on the level of GlcNAc 6-phosphate
PMID:15983044
Scission of the lactyl ether bond of N-acetylmuramic acid by Escherichia coli "etherase".
Identifies MurQ as the MurNAc-6P etherase and its products.
catalyze the cleavage of MurNAc 6-phosphate, with GlcNAc 6-phosphate and D-lactate being the primary products
PMID:15901686
Recycling of the anhydro-N-acetylmuramic acid derived from cell wall murein involves a two-step conversion to N-acetylglucosamine-phosphate.
Shows that anhydro-MurNAc from murein turnover is converted to GlcNAc-P by AnmK followed by the etherase.
The sugar is first phosphorylated by anhydro-N-acetylmuramic acid kinase (AnmK), yielding MurNAc-P, and this is followed by action of an etherase
PMID:18723630
The transcriptional factors MurR and catabolite activator protein regulate N-acetylmuramic acid catabolism in Escherichia coli.
Establishes MurR as the MurNAc-6P-responsive repressor of murQ.
MurNAc-6-phosphate, the substrate of MurQ, was identified as a specific inducer that weakens binding of MurR to the operator.
PMID:35640608
Molecular basis for cell-wall recycling regulation by transcriptional repressor MurR in Escherichia coli.
Structural and biochemical confirmation of MurNAc-6P as the MurR inducer.
In this work, we revealed that MurNAc-6-P directly binds to MurR to induce the dissociation of MurR from the promoter DNA, leading to the derepression of the murPQ pathway.
RHEA:26410
MurQ reaction
Defines the EC 4.2.1.126 MurNAc-6P etherase reaction.
RHEA:24952
AnmK reaction
Defines ring opening and phosphorylation of anhydro-MurNAc to MurNAc-6P.
RHEA:33399
MurP reaction
Defines PTS-coupled uptake and 6-phosphorylation of MurNAc (EC 2.7.1.192).

Grounded on Escherichia coli K-12, where every step has direct genetic and biochemical evidence (gene reviews genes/ECOLI/murP, murQ and murR). Bacillus subtilis representatives are included where reviewed or curated: MurQ (Q45582) and the MurR-like repressor YbbH (Q45581, genes/BACSU/ybbH), whose regulator role is supported by a murR deletion reporter but whose DNA binding and effector are inferred from E. coli MurR. E. coli MurR also represses pbp4B, which is not modeled. The EIIA-Glc (Crr), HPr and enzyme I phosphoryl relay that feeds MurP is shared with the glucose PTS and is context rather than a part of this module. GO has no term for the MurQ etherase activity or for negative regulation of MurNAc catabolism; both are proposed as new terms in the murQ and murR reviews, so the MurQ annoton carries no GO id.

6Nodes
3Parts
1Variant Sets
2Variants
4Annotons
3Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:murnac_6p_catabolic_recycling deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Reaction chaining (advisory)

✓ every PRECEDES step chains, or its break is acknowledged via chaining_status.

  • murnac_6p_formation → murQ_etherase_step [NOT_CHECKED]
    Both MurP and AnmK produce MurNAc-6P, the MurQ substrate.

Function consistency and core coverage

2 gene-function check(s) reflected in core functions · 0 conflict(s) · 7 evidence or coverage gap(s) (9 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

AnnotonParticipantFunctionAssessment
murP_activity murP (Escherichia coli K-12)
UniProtKB:P77272
Family Representative 		protein-phosphocysteine-N-acetylmuramate phosphotransferase system transporter activity
GO:0090588 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
anmK_activity anmK (Escherichia coli K-12)
UniProtKB:P77570
Family Representative 		1,6-anhydro-N-acetylmuramic acid kinase activity
GO:0016773 		Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
murQ_activity murQ (Escherichia coli K-12)
UniProtKB:P76535
Family Representative 		N-acetylmuramic acid 6-phosphate etherase activity
No function ID 		No Function Id
A gene review exists, but this function lacks a GO identifier. Free-text chemistry is not automatically compared.
murQ_activity murQ / ybbI (Bacillus subtilis 168)
UniProtKB:Q45582
Family Representative 		N-acetylmuramic acid 6-phosphate etherase activity
No function ID 		Review Missing
No ai-review exists for this protein; its function and core-function coverage cannot yet be checked. The module function also lacks a GO identifier.
murR_activity murR (Escherichia coli K-12)
UniProtKB:P77245
Family Representative 		ligand-modulated transcription repressor activity
GO:0141096 		Core Supported
The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
murP_activity MurNAc-specific PTS EIIBC components
PANTHER:PTHR30175:SF3
Family 		protein-phosphocysteine-N-acetylmuramate phosphotransferase system transporter activity
GO:0090588 		Family Review Missing
No supported structured family review is available for PANTHER:PTHR30175:SF3.
anmK_activity AnmK family
PANTHER:PTHR30605:SF0
Family 		1,6-anhydro-N-acetylmuramic acid kinase activity
GO:0016773 		Family Review Missing
No supported structured family review is available for PANTHER:PTHR30605:SF0.
murQ_activity MurQ MurNAc-6P etherases
Family 		N-acetylmuramic acid 6-phosphate etherase activity
No function ID 		No Function Id
The family function has no GO identifier for comparison; prose is not matched.
murR_activity MurR RpiR-family repressors
PANTHER:PTHR30514:SF17
Family 		ligand-modulated transcription repressor activity
GO:0141096 		Family Review Missing
No supported structured family review is available for PANTHER:PTHR30514:SF17.

Feedback loops (advisory, prose-driven: a regulator counts as "feedback" when its own description says so)

✓ every negative regulator described as feedback has an upstream edge closing the loop.

  • murR_repression_step ⊣ murQ_etherase_step [input]
    murR_repression_step is a negative regulator with no upstream edge (not described as feedback)

Gene-review completeness (3/5 grounded genes reviewed)

3 complete review(s) · 0 with deep research · 2 missing review · 3 reviewed but lacking deep research

Gene Review Complete Deep research
murP P77272 ✓ ✓ ✗
murQ P76535 ✓ ✓ ✗
murR P77245 ✓ ✓ ✗
anmK (Escherichia coli K-12) P77570 ✗ — —
murQ / ybbI (Bacillus subtilis 168) Q45582 ✗ — —

Details

MurNAc 6-phosphate etherase route of muramic acid recyclingMetabolic Pathwaymurnac_6p_catabolic_recycling
N-acetylmuramic acid catabolic processGO:0097173 1,6-anhydro-N-acetyl-beta-muramic acid catabolic processGO:0097175 peptidoglycan turnoverGO:0009254

Connections

murR_repression_step -> murQ_etherase_step Negatively Regulates
Part 1: MurNAc 6-phosphate formation
MurNAc 6-phosphate formationReactionmurnac_6p_formation
Variant set: source of MurNAc 6-phosphate by MurNAc substrate form (One Or More)
PTS uptake and phosphorylation of free MurNAcTransport StepmurP_pts_uptake_variant

Annotons

MurNAc-specific PTS EIIBC
murP_activity
Participant: Family: MurNAc-specific PTS EIIBC components
Family:
MurNAc-specific PTS EIIBC componentsPANTHER:PTHR30175:SF3
Representative Members: murP (Escherichia coli K-12)UniProtKB:P77272

Function

protein-phosphocysteine-N-acetylmuramate phosphotransferase system transporter activityGO:0090588
Substrates: N-acetylmuramate (periplasmic) N(pros)-phospho-L-histidyl-[EIIA-Glc]
Products: N-acetylmuramate 6-phosphate (cytoplasmic) L-histidyl-[EIIA-Glc]

Processes

phosphoenolpyruvate-dependent sugar phosphotransferase systemGO:0009401

Locations

plasma membraneGO:0005886

Imports free MurNAc as MurNAc-6P.

AnmK phosphorylation of recycled anhydro-MurNAcReactionanmK_variant

Annotons

Anhydro-N-acetylmuramic acid kinase
anmK_activity
Participant: Family: AnmK family
Family:
AnmK familyPANTHER:PTHR30605:SF0
Representative Members: anmK (Escherichia coli K-12)UniProtKB:P77570

Function

1,6-anhydro-N-acetylmuramic acid kinase activityGO:0016773
Substrates: 1,6-anhydro-N-acetylmuramic acid ATP water
Products: N-acetylmuramate 6-phosphate ADP

Processes

1,6-anhydro-N-acetyl-beta-muramic acid catabolic processGO:0097175

Converts anhydro-MurNAc from imported turnover fragments to MurNAc-6P. The same reaction feeds MupP in the Pseudomonas anabolic route.

Part 2: MurNAc 6-phosphate lactyl ether cleavage
MurQ cleavage of MurNAc 6-phosphateReactionmurQ_etherase_step

Annotons

N-acetylmuramic acid 6-phosphate etherase
murQ_activity
Participant: Family: MurQ MurNAc-6P etherases
Family:
MurQ MurNAc-6P etherases
Representative Members: murQ (Escherichia coli K-12)UniProtKB:P76535 murQ / ybbI (Bacillus subtilis 168)UniProtKB:Q45582

Function

N-acetylmuramic acid 6-phosphate etherase activity
Substrates: N-acetylmuramate 6-phosphate water
Products: N-acetyl-D-glucosamine 6-phosphate (R)-lactate

Processes

N-acetylmuramic acid catabolic processGO:0097173 1,6-anhydro-N-acetyl-beta-muramic acid catabolic processGO:0097175 peptidoglycan turnoverGO:0009254

Common step of both MurNAc-6P sources; releases GlcNAc-6P into the GlcNAc catabolic pathway and D-lactate.

Part 3: MurNAc 6-phosphate-responsive repression of murPQ
MurR repression of murP-murQ transcriptionRegulatory StepmurR_repression_step

Annotons

MurR ligand-modulated transcription repressor
murR_activity
Participant: Family: MurR RpiR-family repressors
Family:
MurR RpiR-family repressorsPANTHER:PTHR30514:SF17
Representative Members: murR (Escherichia coli K-12)UniProtKB:P77245

Function

ligand-modulated transcription repressor activityGO:0141096

Processes

negative regulation of DNA-templated transcriptionGO:0045892 negative regulation of carbohydrate utilizationGO:0180068

Senses the pathway intermediate MurNAc-6P and derepresses murP-murQ when it accumulates. The B. subtilis homolog YbbH (Q45581) has a repressor role shown by deletion but an inferred operator and effector, so it is noted rather than listed as a representative.