title: Modulation of the kinetics and the steady-state level of intermediates of mitochondrial coupled reactions by inhibitors and uncouplers.
abstract: In oxidative phosphorylation and ATP-driven uphill electron transfer from succinate to NAD, double-reciprocal plots of rates vs. substrate concentrations of the energy-driven reactions are a family of parallel lines at several fixed subsaturating concentrations of the substrates or at several moderate concentrations of the inhibitors of the energy-yielding reactions. Thus, as shown elsewhere [Hatefi, Y., Yagi, T., Phelps, D. C., Wong, S.-Y., Vik, S. B., & Galante, Y. M. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 1756-1760], partial uncoupling decreases the Vappmax and increases the Kappm of the substrates of the energy-driven reactions, resulting in a decrease of Vmax/Km as a function of increased uncoupling. However, partial limitation of the flow rates of the energy-yielding reactions decreases both the Vappmax and the Kappm of the substrates of the energy-driven reactions, resulting in no change in Vmax/Km. This is true as long as the rate limitation is moderate (e.g., less than 60%), under which conditions the steady-state membrane potential (delta psi) remains essentially unchanged. At high inhibition of the energy-yielding reactions, or at moderate inhibition in the presence of low levels of an uncoupler to cause partial uncoupling, then the family of double-reciprocal plots is no longer parallel and tends to converge toward the left. Under these conditions, steady-state delta psi and Vmax/Km also decrease as inhibition is increased. The relationship between the magnitude of steady-state delta psi and the rate of the energy-driven reaction was studied in oxidative phosphorylation, ATP-driven electron transfer from succinate to NAD, and respiration-driven uniport calcium transport by intact mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002417:Cattle; D007700:Kinetics; D008314:Malonates / Q000494:pharmacology; D008929:Mitochondria, Heart / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects; D012402:Rotenone / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D001386:Azides; D008314:Malonates; D009840:Oligomycins; D014475:Uncoupling Agents; D012402:Rotenone; D009243:NAD; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000255:Adenosine Triphosphate; C030290:malonic acid; D002118:Calcium