Vacuolar H(+)-pyrophosphatase.
The H(+)-translocating inorganic pyrophosphatase (H(+)-PPase) is a unique, electrogenic proton pump distributed among most land plants, but only some alga, protozoa, bacteria, and archaebacteria. This enzyme is a fine model for research on the coupling mechanism between the pyrophosphate hydrolysis and the active proton transport, since the enzyme consists of a single polypeptide with a calculated molecular mass of 71-80 kDa and its substrate is also simple. Cloning of the H(+)-PPase genes from several organisms has revealed the conserved regions that may be the catalytic site and/or participate in the enzymatic function. The primary sequences are reviewed with reference to biochemical properties of the enzyme, such as the requirement of Mg(2)(+) and K(+). In plant cells, H(+)-PPase coexists with H(+)-ATPase in a single vacuolar membrane. The physiological significance and the regulation of the gene expression of H(+)-PPase are also reviewed.
Maeshima
M
M
Laboratory of Biochemistry, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan. maeshima@agr.nagoya-u.ac.jp
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D043564:Inorganic Pyrophosphatase; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014617:Vacuoles / Q000201:enzymology*
D008565:Membrane Proteins; D010940:Plant Proteins; D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase