title: Requirement of medium ADP for the steady-state hydrolysis of ATP by the proton-translocating Paracoccus denitrificans Fo.F1-ATP synthase.
abstract: Fo.F1-ATP synthase in inside-out coupled vesicles derived from Paracoccus denitrificans catalyzes Pi-dependent proton-translocating ATPase reaction if exposed to prior energization that relieves ADP.Mg2+ -induced inhibition (Zharova, T.V. and Vinogradov, A.D. (2004) J. Biol. Chem.,279, 12319-12324). Here we present evidence that the presence of medium ADP is required for the steady-state energetically self-sustained coupled ATP hydrolysis. The initial rapid ATPase activity is declined to a certain level if the reaction proceeds in the presence of the ADP-consuming, ATP-regenerating system (pyruvate kinase/phosphoenol pyruvate). The rate and extent of the enzyme de-activation are inversely proportional to the steady-state ADP concentration, which is altered by various amounts of pyruvate kinase at constant ATPase level. The half-maximal rate of stationary ATP hydrolysis is reached at an ADP concentration of 8 x 10(-6) M. The kinetic scheme is proposed explaining the requirement of the reaction products (ADP and Pi), the substrates of ATP synthesis, in the medium for proton-translocating ATP hydrolysis by P. denitrificans Fo.F1-ATP synthase.
authors.affiliation: Department of Biochemistry, School of Biology, Moscow State University, Moscow 119992, Russian Federation.
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Zharova
authors.forename: Andrei D
authors.initials: AD
authors.lastname: Vinogradov
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D025243:Bacterial Proton-Translocating ATPases / Q000378:metabolism*; D002417:Cattle; D004789:Enzyme Activation; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D010231:Paracoccus denitrificans / Q000201:enzymology*; D011770:Pyruvate Kinase / Q000378:metabolism
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D011770:Pyruvate Kinase; D025243:Bacterial Proton-Translocating ATPases