||Fraichard A, Trossat C, Perotti E, Pugin A. Allosteric regulation by Mg2+ of the vacuolar H(+)-PPase from Acer pseudoplatanus cells. Ca2+/Mg2+ interactions. Biochimie. 1996 78(4):259-66. p.265 left column bottom paragraphPubMed ID8874801
||Hendrik Weiner, Mark Stitt, Hans W. Heldt, Subcellular compartmentation of pyrophosphate and alkaline pyrophosphatase in leaves, Biochimica et Biophysica Acta (BBA) - Bioenergetics Volume 893, Issue 1, 12 August 1987, Pages 13–21 link
||The Km value (16µM) and the cytosolic PPi concentration,
about 200µM [primary source], show that the rate of PPi is certainly not limiting in vivo. Plants studied in primary source were spinach leaves and wheat mesophyll protoplasts.