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Kinetics of the membrane‐bound inorganic pyrophosphatase from Rhodospirillum rubrum chromatophores
Author(s) -
Strid Åke,
Nyrén Pål,
Boork Jeff,
Baltscheffsky Margareta
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80274-5
Subject(s) - rhodospirillum rubrum , inorganic pyrophosphatase , chemistry , electrochemical gradient , reaction rate constant , chromatophore , pyrophosphatase , kinetics , hydrolysis , membrane , proton , chemiosmosis , enzyme , photochemistry , atp synthase , biochemistry , biology , pyrophosphate , physics , quantum mechanics , fishery
The behaviour of the membrane‐bound proton‐translocating pyrophosphatase (H + ‐PPase) in Rhodospirillum rubrum chromatophores upon application of an electrochemical potential is studied. The rate constants are shown to be affected in an asymmetric fashion. The forward rate constant (PP i synthesis) is shown to be at least 45‐times larger during illumination than when there is no proton‐motive force. The hydrolysis rate is increased maximally 8‐times when the potential is dissipated. The effect of the electrical field gradient is thus mainly to increase the forward rate of the reaction. The H + ‐PPase also seems to be a functionally simpler enzyme than the H + ‐ATPase, lacking the hydrolysis activation step during energization found in the latter.