title: Dynamic disorder in quasi-equilibrium enzymatic systems.
abstract: Conformations and catalytic rates of enzymes fluctuate over a wide range of timescales. Despite these fluctuations, there exist some limiting cases in which the enzymatic catalytic rate follows the macroscopic rate equation such as the Michaelis-Menten law. In this paper we investigate the applicability of macroscopic rate laws for fluctuating enzyme systems in which catalytic transitions are slower than ligand binding-dissociation reactions. In this quasi-equilibrium limit, for an arbitrary reaction scheme we show that the catalytic rate has the same dependence on ligand concentrations as obtained from mass-action kinetics even in the presence of slow conformational fluctuations. These results indicate that the timescale of conformational dynamics--no matter how slow--will not affect the enzymatic rate in quasi-equilibrium limit. Our numerical results for two enzyme-catalyzed reaction schemes involving multiple substrates and inhibitors further support our general theory.
authors.affiliation: Department of Bioengineering, Rice University, Houston, Texas, United States of America.
authors.forename: Srabanti
authors.initials: S
authors.lastname: Chaudhury
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Igoshin
mesh_terms: D000494:Allosteric Regulation; D055162:Biocatalysis; D003067:Coenzymes / Q000737:chemistry / Q000378:metabolism; D004798:Enzymes / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008956:Models, Chemical
chemical_list: D003067:Coenzymes; D004798:Enzymes
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