InterPro: IPR004131 Inorganic H+ pyrophosphatase

Two types of proteins that hydrolyse inorganic pyrophosphate (PPi), very different in both amino acid sequence and structure, have been characterised to date: soluble and membrane-bound proton-pumping pyrophosphatases (sPPases and H(⁺)-PPases, respectively). sPPases are ubiquitous proteins that hydrolyse PPi to release heat, whereas H⁺-PPases, so far unidentified in animal and fungal cells, couple the energy of PPi hydrolysis to proton movement across biological membranes [1, 2]. The latter type is represented by this group of proteins. H⁺-PPases (EC:3.6.1.1) are also called vacuolar-type inorganic pyrophosphatases (V-PPase) or pyrophosphate-energised vacuolar membrane proton pumps [3]. In plants, vacuoles contain two enzymes for acidifying the interior of the vacuole, the V-ATPase and the V-PPase (V is for vacuolar) [2].

Two distinct biochemical subclasses of H⁺-PPases have been characterised to date: K⁺-stimulated and K⁺-insensitive [1, 3].

For additional information please see [4, 5].