InterPro domain: IPR030673

This entry includes guanosine-5'-triphosphate,3'-diphosphate pyrophosphatases (also known as pppGpp-5'-phosphohydrolases) and exopolyphosphatases.

Exopolyphosphatases (Ppx) is involved in the degradation of inorganic polyphosphates [ 1 ] and belongs to the same family as the guanosine pentaphosphate phosphatase [ 2 ].

Guanosine pentaphosphate (pppGpp) is a cytoplasmic signaling molecule which together with ppGpp controls the "stringent response", an adaptive process that allows bacteria to respond to amino acid starvation, resulting in the coordinated regulation of numerous cellular activities. Guanosine-5'-triphosphate,3'-diphosphate pyrophosphatase (GppA), also known as guanosine pentaphosphate phosphohydrolase, catalyses the conversion of pppGpp to ppGpp.

1. An exopolyphosphatase of Escherichia coli. The enzyme and its ppx gene in a polyphosphate operon. J. Biol. Chem. 268, 633-9
2. Exopolyphosphate phosphatase and guanosine pentaphosphate phosphatase belong to the sugar kinase/actin/hsp 70 superfamily. Trends Biochem. Sci. 18, 247-8