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Product complex
Human PKM2 allosteric regulation and catalysis: Dombrauckas JD et al., Biochemistry 2005, PMID:15996096 (1T5A, FBP + oxalate). FBP-bound M2PYK R-state structures and nutrient-sensing mechanism: Morgan HP et al., PNAS 2013, PMID:23530218. Note: the scaffold in the viewer is 3SRD, a related FBP+oxalate M2 deposition that itself has no standalone PMID; the mechanism and ligand set are those in the cited published literature.
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① PEP binds — Lys270 neutralizes carboxylate
[schematic] PEP enters with Lys270 neutralizing its carboxylate while Asp296 coordinates Mg²⁺, positioning the enol-phosphate for transfer (pose snapped into the real oxalate/pyruvate-analog slot).
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② ADP binds — Michaelis assembly
[schematic] ADP docks with its β-phosphate facing PEP's phosphate; Mg²⁺ chelates the α,β-phosphates and Lys270 stabilizes the β oxygens for in-line attack.
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③ S_N2 phosphoryl transfer
[schematic] The ADP β-oxygen attacks PEP's phosphorus in-line (S_N2) while the P–O bond to the enol carbon breaks in the same step — no covalent intermediate; Mg²⁺ stabilizes the developing enolate (snaps PEP→oxalate, ADP→ATP).
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④ Enol → keto tautomerization
[schematic] The enol-pyruvate tautomerizes to the stable keto pyruvate via a water-mediated proton relay in the closed active site.
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⑤ Products release
Pyruvate (oxalate-analog position) and ATP dissociate — the second ATP payoff; per glucose, PK yields 2 pyruvate + 2 ATP.
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Sequence
DNA/gene NCBI Gene 5315 · protein UniProt P14618
› Backbones and ligand poses are taken directly from the listed PDB entries,
superposed into one common frame. Where no crystalline state exists for a step
(e.g., Michaelis geometry), the pose is drawn schematically using PubChem 3D
geometries and is labeled as such in the narration.