| Topic | Key findings | Evidence source (author/year/title) | Publication date | URL/DOI when available | Citation ID(s) |
|---|---|---|---|---|---|
| Identity | UniProt Q88QT2 corresponds to **murU / PP_0406** in *Pseudomonas putida* KT2440 and is described as **N-acetylmuramate alpha-1-phosphate uridylyltransferase**; pathway literature consistently uses MurU for the MurNAc salvage/MurU shunt enzyme. | Richter et al. 2026, *Peptidoglycan recycling is critical for cell division, cell wall integrity, and β-lactam resistance in Caulobacter crescentus*; Hyland et al. 2024, *Bioorthogonal Labeling and Click-Chemistry-Based Visualization of the Tannerella forsythia Cell Wall* | 2026 Apr; 2024 Oct | https://doi.org/10.7554/eLife.109465 ; https://doi.org/10.1007/978-1-0716-3491-2_1 | (pqac-00000004, pqac-00000006) |
| Enzymatic reaction | MurU acts **downstream of AmgK** and converts **MurNAc monophosphate intermediates to UDP-MurNAc products**, i.e. the uridylyltransferase step that regenerates UDP-MurNAc for PG precursor synthesis. | Liang 2018 thesis, *…labeling of the carbohydrate core in bacterial peptidoglycan via the Pseudomonas putida cell wall recycling enzymes AmgK and MurU and its applications* | 2018 | Not available in snippet; cites Nat Commun 2017 in thesis | (pqac-00000001, pqac-00000009, pqac-00000010) |
| Substrate specificity | Purified *P. putida* AmgK/MurU accepted natural NAM and several modified NAM derivatives. MurU converted monophosphate intermediates **1–8** to UDP products; Table 4 indicates MurU accepted substrates generated from 2-azido-, 2-alkyne-, ketone-, and some photo-crosslinking derivatives, but not all bulky probes (e.g., streptavidin-affinity probes). | Liang 2018 thesis, *…labeling of the carbohydrate core in bacterial peptidoglycan via the Pseudomonas putida cell wall recycling enzymes AmgK and MurU and its applications* | 2018 | Not available in snippet | (pqac-00000009, pqac-00000010) |
| Pathway role | MurU is part of a **MurNAc salvage / peptidoglycan recycling shortcut** that provides another route to **UDP-MurNAc** from NAM, bypassing de novo MurA/B-dependent synthesis. In Gram-negative recycling, muropeptides are typically imported by **AmpG**, processed in the cytoplasm, and in MurU-pathway organisms the MurNAc-derived intermediate is returned to UDP-MurNAc. | Liang 2018 thesis, Figure 1.4 description and chapter text; Richter et al. 2026 eLife background | 2018; 2026 Apr | https://doi.org/10.7554/eLife.109465 | (pqac-00000008, pqac-00000005) |
| Localization inference | No direct localization experiment for *P. putida* MurU was present in the snippets, but pathway context supports a **cytosolic** role: recycled muropeptides are transported into the cytoplasm via AmpG, then separated/processed, and MurU uses MurNAc-phosphate intermediates to generate UDP-MurNAc for the cytoplasmic precursor pathway. | Richter et al. 2026, *Peptidoglycan recycling is critical…*; Liang 2018 thesis pathway context | 2026 Apr; 2018 | https://doi.org/10.7554/eLife.109465 | (pqac-00000005, pqac-00000008) |
| Applications | The *P. putida* AmgK/MurU system was exploited to generate **UDP-MurNAc probes** and to enable **metabolic labeling of bacterial peptidoglycan** with azido/alkyne NAM analogs, supporting fluorescence imaging, SIM/STORM, macrophage interaction studies, and production of labeled PG fragments. Related methods papers use heterologous AmgK/MurU expression to label PG in other organisms. | Liang 2018 thesis; Hyland et al. 2024, *Bioorthogonal Labeling and Click-Chemistry-Based Visualization of the Tannerella forsythia Cell Wall* | 2018; 2024 Oct | https://doi.org/10.1007/978-1-0716-3491-2_1 | (pqac-00000002, pqac-00000012, pqac-00000006) |
| Quantitative data | For the partner kinase **AmgK** in the same *P. putida* pathway, reported kinetics with NAM were **Km = 30.41 ± 5.75 μM** and **kcat = 6.58 ± 0.21 s^-1**; 2Az-NAM and 2Alk-NAM showed about **10-fold lower efficiency** than NAM. In cell assays, **0.2% (w/v)** NAM analogs restored growth of engineered *E. coli* under **200 μg/mL fosfomycin**. These data support flux through the AmgK→MurU salvage route, though MurU-specific kinetics were not given in the snippets. | Liang 2018 thesis, kinetic and growth sections | 2018 | Not available in snippet | (pqac-00000010, pqac-00000012) |
| Phenotype/pathway context | Pathway perturbation phenotypes in other bacteria support biological importance of MurU-shunt recycling. In *A. baumannii*, disrupting recycling enzymes increased fosfomycin susceptibility and altered fitness/virulence traits; under the reported conditions morphology was unchanged, interpreted as de novo synthesis still supplying UDP-MurNAc. | Tajuelo et al. 2023, *Role of peptidoglycan recycling enzymes AmpD and AnmK in Acinetobacter baumannii virulence features* | 2023 Jan | https://doi.org/10.3389/fcimb.2022.1064053 | (pqac-00000007) |


*Table: This table summarizes the key evidence supporting functional annotation of MurU (Q88QT2/PP_0406) in Pseudomonas putida KT2440, including its enzymatic role, pathway placement, inferred localization, applications, and available quantitative support. It is restricted to findings present in the provided evidence snippets.*