9ej2
From Proteopedia
Rat cytosolic PEPCK in complex with GTP and oxalate (313K)
Structural highlights
FunctionPCKGC_RAT Catalyzes the conversion of oxaloacetate (OAA) to phosphoenolpyruvate (PEP), the rate-limiting step in the metabolic pathway that produces glucose from lactate and other precursors derived from the citric acid cycle. Publication Abstract from PubMedEnzyme activity varies with temperature. Unlike small-molecule catalysts, the structural ensembles of enzymes can change substantially with temperature, but it is unclear how this modulates temperature dependent activity. Here, multi-temperature X-ray crystallography was used to record structural changes from -20 degrees C to 40 degrees C for a mesophilic enzyme in complex with inhibitors mimicking substrate-, intermediate-, and product-bound states, representative of major complexes on the reaction coordinate. Inhibitors, substrates and active site loops increasingly populated catalytically competent conformations as temperature increased. These changes occurred even in temperature ranges where kinetic measurements showed roughly linear Arrhenius/Eyring behavior, where parameters characterizing the system are assumed to be temperature independent. Simple analysis shows that linear Arrhenius/Eyring behavior can still be observed when the underlying activation energy/enthalpy values vary with temperature. Our results indicate a critical role for temperature dependent atomic-resolution structural data in interpreting temperature dependent kinetic data from enzymatic systems. A structural perspective on the temperature dependent activity of enzymes.,McLeod MJ, Barwell SAE, Holyoak T, Thorne RE Structure. 2025 Mar 17:S0969-2126(25)00093-0. doi: 10.1016/j.str.2025.02.013. PMID:40120576[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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