3PCF:
reference: Structures of competitive inhibitor complexes of protocatechuate 3,4-dioxygenase: multiple exogenous ligand binding orientations within the active site., Orville AM, Elango N, Lipscomb JD, Ohlendorf DH, Biochemistry 1997 Aug 19;36(33):10039-51. PMID: 9254599

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