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AmgK phosphorylates MurNAc at the anomeric carbon (C1) to produce MurNAc-alpha-1-phosphate, the committed intermediate of the MurU-dependent anabolic peptidoglycan recycling pathway.
"phosphorylates **N-acetylmuramic acid (MurNAc/NAM)** at the **anomeric carbon (C1)** to produce **MurNAc-α-1-phosphate (MurNAc-1P)**, a committed intermediate of a **MurU-dependent anabolic peptidoglycan (PG) recycling pathway** that regenerates **UDP-MurNAc** for cell wall synthesis."
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The recycling pathway bypasses the de novo MurA/MurB route and confers intrinsic fosfomycin resistance, since fosfomycin targets MurA.
"This recycling “shortcut” bypasses the canonical **MurA/MurB** de novo pathway and contributes to **intrinsic fosfomycin resistance** in pseudomonads because fosfomycin targets MurA."
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AmgK is an anomeric MurNAc/GlcNAc kinase generating C1-phosphorylated sugars from both MurNAc and GlcNAc.
"AmgK is also described as an **anomeric MurNAc/GlcNAc kinase**, and experimental workflows use AmgK to generate **C1-phosphorylated sugars** from MurNAc and GlcNAc substrates."
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MurNAc accumulates in a P. putida amgK deletion mutant, confirming AmgK is required for the MurNAc phosphorylation step of the salvage route.
"A key organism-specific observation in *P. putida* is that **MurNAc accumulates in a ΔamgK mutant**, consistent with AmgK being required to phosphorylate MurNAc in the salvage route."
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AmgK acts downstream of MupP in the anabolic recycling route, converting MurNAc to MurNAc-1P for MurU to form UDP-MurNAc.
"AmgK is positioned after MupP in the anabolic pathway: MupP generates MurNAc from MurNAc-6P, and **AmgK then converts MurNAc into MurNAc-1P** for MurU to form UDP-MurNAc."
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AmgK is inferred to act in the cytoplasm, consistent with the cytosolic processing of imported peptidoglycan fragments.
"This supports the inference that AmgK functions in the **cytoplasm**."