title: Asymmetric effect of mechanical stress on the forward and reverse reaction catalyzed by an enzyme.
abstract: The concept of modulating enzymatic activity by exerting a mechanical stress on the enzyme has been established in previous work. Mechanical perturbation is also a tool for probing conformational motion accompanying the enzymatic cycle. Here we report measurements of the forward and reverse kinetics of the enzyme Guanylate Kinase from yeast (Saccharomyces cerevisiae). The enzyme is held in a state of stress using the DNA spring method. The observation that mechanical stress has different effects on the forward and reverse reaction kinetics suggests that forward and reverse reactions follow different paths, on average, in the enzyme's conformational space. Comparing the kinetics of the stressed and unstressed enzyme we also show that the maximum speed of the enzyme is comparable to the predictions of the relaxation model of enzyme action, where we use the independently determined dissipation coefficient [Formula: see text] for the enzyme's conformational motion. The present experiments provide a mean to explore enzyme kinetics beyond the static energy landscape picture of transition state theory.
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Collin
authors.initials: C
authors.lastname: Joseph
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Chiao-Yu
authors.initials: CY
authors.lastname: Tseng
authors.affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Zocchi
authors.affiliation: Institute for Advanced Study, Princeton, New Jersey, United States of America.
authors.forename: Tsvi
authors.initials: T
authors.lastname: Tlusty
mesh_terms: D055162:Biocatalysis / Q000187:drug effects; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051528:Guanylate Kinases / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013314:Stress, Mechanical; D013816:Thermodynamics
chemical_list: D004247:DNA; D051528:Guanylate Kinases; D008274:Magnesium