4B2D:
reference: Serine is a natural ligand and allosteric activator of pyruvate kinase M2., Chaneton B, Hillmann P, Zheng L, Martin AC, Maddocks OD, Chokkathukalam A, Coyle JE, Jankevics A, Holding FP, Vousden KH, Frezza C, O'Reilly M, Gottlieb E, Nature. 2012 Oct 14. doi: 10.1038/nature11540. PMID: 23064226

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