The H+ pyrophosphatase is an transmembrane proton pump involved in establishing the H+ electrochemical potential difference between the vacuole lumen and the cell cytosol. Vacuolar-type H(+)-translocating inorganic pyrophosphatases have long been considered to be restricted to plants and to a few species of photo-trophic bacteria. However, in recent investigations, these pyrophosphatases have been found in organisms as disparate as thermophilic Archaea and parasitic protists [1].

1: Vacuolar H(+) pyrophosphatases: from the evolutionary backwaters into the mainstream. Drozdowicz YM, Rea PA; Trends Plant Sci 2001;6:206-211. PMID:11335173