3BJM:
reference: Involvement of DPP-IV catalytic residues in enzyme-saxagliptin complex formation., Metzler WJ, Yanchunas J, Weigelt C, Kish K, Klei HE, Xie D, Zhang Y, Corbett M, Tamura JK, He B, Hamann LG, Kirby MS, Marcinkeviciene J, Protein Sci. 2008 Feb;17(2):240-50. PMID: 18227430

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