3NOJ:
reference: Structural and kinetic characterization of 4-hydroxy-4-methyl-2-oxoglutarate (HMG)/4-carboxy-4-hydroxy-2-oxoadipate (CHA) aldolase: a protocatechuate degradation enzyme evolutionarily convergent with the HpaI and DmpG pyruvate aldolases., Wang W, Mazurkewich S, Kimber MS, Seah SY, J Biol Chem. 2010 Sep 15. PMID: 20843800

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