title: The reaction process of firefly bioluminescence triggered by photolysis of caged-ATP.
abstract: The reaction process of firefly bioluminescence was studied by photolyzing caged-ATP to adenosine triphosphate (ATP) within 100 ms. The intensity of luminescence increases markedly to reach a maximum within 1 s, maintains almost the same intensity up to 5 s and then decays monotonically. The rise γ(1) and decay γ(2) rate constants were determined to be about 5 s(-1) and 1 × 10(-2) s(-1), respectively, so as to phenomenologically fit the time course. A second luminescence peak appears after around 350 s. The dependence of the rate constants on the concentrations of reactants and a viscous reagent revealed that two kinds of reaction contribute the observed time course: (1) an intrinsic reaction by ATP photolyzed from caged-ATP that is already trapped in luciferase; and (2) a diffusion-controlled reaction by free ATP in the buffer solution outside luciferase. Numerical analysis based on reaction kinetics related γ(1) and γ(2) to the rate constants of a three-step reaction model, and accurately described the effects of concentration of reactants and a viscous reagent on the time courses of bioluminescence. Thus, it has been clearly concluded that the binding mode of caged-ATP at the catalytic center of luciferase is very different from that of ATP.
authors.affiliation: Department of Physics, Faculty of Engineering, Yokohama National University, Hodogaya-ku, Yokohama, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kageyama
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Tanaka
authors.forename: Takao
authors.initials: T
authors.lastname: Sekiya
authors.forename: Shin-Ya
authors.initials: SY
authors.lastname: Ohno
authors.forename: Naohisa
authors.initials: N
authors.lastname: Wada
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D004058:Diffusion / Q000528:radiation effects; D048888:Fireflies; D007700:Kinetics; D008027:Light; D008156:Luciferases / Q000378:metabolism*; D049449:Luminescence; D008164:Luminescent Proteins / Q000378:metabolism*; D010782:Photolysis / Q000528:radiation effects; D014783:Viscosity
chemical_list: D008164:Luminescent Proteins; D000255:Adenosine Triphosphate; D008156:Luciferases