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H^+^/PP~i~ stoichiometry of a membrane‐bound pyrophosphatase of plant mitochondria by Marco Zancani; Valentino Casolo; Angelo Vianello; Francesco Macrí is a Agricultural and Biological Sciences article available to read on EtoBox.

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The H^+^/PP~i~ stoichiometry of the mitochondrial H^+^‐PP~i~ase from pea (__Pisum sativum__ L.) stem was determined by two kinetic approaches, and compared with the H^+^/substrate stoichiometries of the mitochondrial H^+^‐ATPase, and the vacuolar H^+^‐PP~i~ase and H^+^‐ATPase. Using sub‐mitochondrial particles or preparations enriched in vacuolar membranes, the rates of substrate‐dependent H^+^‐transport were evaluated: by a mathematical model, describing the time‐course of H^+^‐gradient (ΔpH) formation; or by determining the rate of H^+^‐leakage following H^+^‐pumping inhibition by EDTA at the steady‐state ΔpH. When the H^+^‐transport rates were divided by those of PP~i~ or ATP hydrolysis, measured under identical conditions, apparent stoichiometries of ca 2 were determined for the mitochondrial H^+^‐PP~i~ase and H^+^‐ATPase, and for the vacuolar H^+^‐ATPase. The stoichiometry of the vacuolar H^+^‐PP~i~ase was found to be ca 1. From these results, it is suggested that the mitochondrial H^+^‐PP~i~ase may, in theory, function as a primary H^+^‐pump poised towards synthesis of PP~i~ and, therefore, acting in parallel with the main H^+^‐ATPase.

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Author

Marco Zancani; Valentino Casolo; Angelo Vianello; Francesco Macrí

Publisher

John Wiley and Sons; Wiley (Blackwell Publishing); Blackwell Publishing Inc.; Wiley (ISSN 0031-9317)

Published

1998

Language

EN

Field

Agricultural and Biological Sciences (Life Sciences)