Premium
Proton pumping pyrophosphatase from higher plant mitochondria
Author(s) -
Vianello Angelo,
Macrì Francesco
Publication year - 1999
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1999.105422.x
Subject(s) - inorganic pyrophosphatase , pyrophosphatase , electrochemical gradient , pyrophosphate , chemistry , membrane , inner mitochondrial membrane , pyrophosphatases , inner membrane , enzyme , chemiosmosis , biochemistry , atp synthase , mitochondrion , proton pump , atpase
In higher plant cells, there are some enzymes capable of utilizing pyrophosphate (PP i ) as an energy donor. Among these, membrane‐bound proton pumping pyrophosphatases (H + ‐PP i ase) have been identified. In addition to the well‐known vacuolar H + ‐PP i ase (V‐PP i ase), there is evidence for the presence of a mitochondrial H + ‐PP i ase. This enzyme is localized on the inner surface of the inner membrane and catalyzes the specific hydrolysis of PP i , coupled to proton transport, with a H + /PP i stoichiometry of ca 2. This activity is Mg 2+ ‐requiring, is stimulated by monovalent cations, and is inhibited by Ca 2+ , F − and diphosphonates. The H + ‐PP i ase contains a catalytic head which is constituted by a 35‐kDa protein which is loosely bound to the inner membrane. This protein exhibits a PP i ase activity, stimulated by phospholipids, with characteristics very similar to the membrane‐bound enzyme. The mitochondrial PP i ase is distinct from the V‐PP i ase, because an antibody raised against the 35‐kDa protein does not react with tonoplast membranes. The mitochondrial H + ‐PP i ase seems to have an F‐type structure, similar to the F‐ATP synthase and the membrane‐bound PP i ases from mammalian and yeast mitochondria. It is suggested that, beside synthesizing PP i , this enzyme may act as a buffer for the electrochemical proton gradient, by hydrolyzing PP i, during conditions of oxygen deprivation.