Pyrophosphatase active in both inorganic pyrophosphate hydrolysis and H(+) translocation. diphosphate + H(+)(in) + H2O = 2 H(+)(out) + 2 phosphate Activated by Mg(+) but not by K(+). Inhibited by Ca(2+). Monomer. Ubiquitous. Mostly expressed in cotyledons, roots and flowers. Especially high levels in trichomes, sepals and stamen filaments. Belongs to the H(+)-translocating pyrophosphatase (TC 3.A.10) family. K(+)-insensitive subfamily. It is uncertain whether Met-1, Met-2 or Met-3 is the initiator.