2NOX:
reference: Crystal structure and mechanism of tryptophan 2,3-dioxygenase, a heme enzyme involved in tryptophan catabolism and in quinolinate biosynthesis(,)., Zhang Y, Kang SA, Mukherjee T, Bale S, Crane BR, Begley TP, Ealick SE, Biochemistry. 2007 Jan 9;46(1):145-55. PMID: 17198384

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