title: Effects of activating cations and inhibitor on the allosteric regulation of rabbit muscle pyruvate kinase.
abstract: Rabbit muscle pyruvate kinase (RMPK) requires activating cations for activity, but its activity can be allosterically inhibited. In this study, isothermal titration calorimetry (ITC) was used to examine the different effects of activating cations (K(+) or Mg(2+)) and inhibitor (Phe) on the allosteric regulation of RMPK. The ITC data reveal that the enthalpy change was greater for PEP binding to the active state compared to the inactive state. Meanwhile, the percentage of the active state increased with increasing concentration of K(+) or Mg(2+), whereas increasing Phe concentration had the opposite effect. In addition, we hypothesize that the activation of RMPK involves two processes. First, the interaction of Mg(2+) leads to a more exposed active site of RMPK. The process is rapid and only a small quantity of Mg(2+) can make RMPK transform to the intermediate state. Second, the subsequent binding of K(+) causes a critical orientation of the active site, which plays a more decisive role for PEP binding to RMPK than Mg(2+).
authors.affiliation: Department of Chemistry, Fudan University, Shanghai 200433, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Ting
authors.initials: T
authors.lastname: Yu
authors.forename: Hang
authors.initials: H
authors.lastname: Jiang
authors.forename: Shaoning
authors.initials: S
authors.lastname: Yu
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D002412:Cations / Q000737:chemistry / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D011770:Pyruvate Kinase / Q000737:chemistry* / Q000378:metabolism; D011817:Rabbits; D013816:Thermodynamics
chemical_list: D002412:Cations; D004791:Enzyme Inhibitors; D011770:Pyruvate Kinase
keywords: ADP; Allosteric regulation; ITC; L-Lactic Dehydrogenase from rabbit muscle; LDH type II; NADH; PEP; PK; Phe; Pyruvate kinase; Thermodynamics; adenosine diphosphate; isothermal titration calorimetry; phenylalanine; phosphoenolpyruvate; pyruvate kinase; β-Nicotinamide adenine dinucleotide reduced disodium salt hydrate