Proton pumping inorganic pyrophosphatase of pea stem submitochondrial particles

Pea stem submitochondrial particles have an inorganic pyrophosphatase (pyrophosphate phosphohydrolase, EC 3.6.1.1) which is able to couple PP i hydrolysis with the generation of an inside positive proton gradient. The activity is Mg 2+ -requiring, is stimulated by monovalent cations, inhibited by imidodiphosphate and, partially, by dicyclohexylcarbodiimide, diethylstilbestrol and oligomycin. This mitochondrial H + -PP i ase is distinguishable from the tonoplast H + -PP i ase and appears to be an additional coupling factor, which works in parallel with the well-known H + -ATPase.