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From Proteopedia

Pyruvate kinase is an enzyme that is utilized in process of glycolysis. Its function within glycolysis is to catalyze the last step of the reaction, in which the second ATP and pyruvate are generated. The catalysis happens by transferring the phosphate group from phosphoenolpyruvate (PEP) to ADP. This specific pyruvate kinase is found in the liver of humans, and it was analyzed by researchers at the University of Kansas Medical Center [1]. They found that the protein's affinity for PEP is reduced several days after cell lysis. The study also suggests energetic coupling between two of the cysteine residues at 436 and the N-terminus of the protein. The of pyruvate kinase shows alpha helices (pink) surrounding beta sheets (blue). Its structure in general has a beta-barrel domain-like fold, and its tertiary structure is tetrameric, with four different domains. This structure is very important in the allosteric regulation of the protein; a study from the University of Pavia, Italy, suggests that there is a dramatic conformational change when the pyruvate kinase goes from the T- to the R-state, and all three domains forming each subunit of the tetrameric enzyme undergo simultaneous rotations [2]. Every single subunit and domain interface is modified. The are shown here. The are highlighted in blue; these are found on the outer surface of the protein since they interact with the solvent. The are highlighted in green and are found on the interior of the protein, away from the solvent. (the solvent with which the protein is interacting) are shown within the structure in green, and the non-water parts of the enzyme are shown in purple. The in pyruvate kinase are highlighted by chain: chain A ligands are in white, chain B ligands are in light purple, chain C ligands are in blue, and chain D ligands are in green. The interacting groups are made up of charged residues like aspartate, arginine, glutamate, lysine, and histidine. The were not shown on PDBSum for this particular version of pyruvate kinase, found in the human liver. However, they were shown in a similar form of the protein, activator-bound human pyruvate kinase, which is the structure shown here. The red residues are anionic (i.e., glutamate), the blue residues are cationic (like lysine), and the histidine residues are white. The green and purple are other ligands within the protein.

[1]Holyoak, T. et al. Energetic coupling between an oxidizable cysteine and the phosphorylatable N-terminus of human liver pyruvate kinase. Biochemistry. 2013 Jan 22;52(3):466-76. doi: 10.1021/bi301341r. Epub 2013 Jan 11. [2] Mattevi, A. et al. The allosteric regulation of pyruvate kinase. FEBS Lett. 1996 Jun 24;389(1):15-9.