| Type: | Family | Name: | Histidine phosphatase superfamily, clade-2 |
| Description: | The histidine phosphatase superfamily is so named because catalysis centres on a conserved His residue that is transiently phosphorylatedduring the catalytic cycle. Other conserved residues contribute to a 'phosphate pocket' and interact with the phospho group of substratebefore, during and after its transfer to the His residue. Structure and sequence analyses show that different families contribute differentadditional residues to the 'phosphate pocket' and, more surprisingly, differ in the position, in sequence and in three dimensions, of acatalytically essential acidic residue. The superfamily may be divided into two main branches. The relationship between the two branches isnot evident by (PSI-)BLAST but is clear from more sensitive sequence searches and structural comparisons [].The smaller clade-2 contains predominantly eukaryotic proteins. The catalytic functions of these proteins nclude phytase, glucose-1-phosphataseand multiple inositol polyphosphate phosphatase. The in vivo roles of the mammalian acid phosphatases in clade-2 are not fully understood,although activity against lysophosphatidic acid and tyrosine-phosphorylated proteins has been demonstrated.Acid phosphatases () are a heterogeneous group of proteins that hydrolyse phosphate esters, optimally at low pH. It has been shown [] that a number of acid phosphatases, from both prokaryotes and eukaryotes, share two regions of sequence similarity, each centred around a conserved histidine residue. These two histidines seem to be involved in the enzymes' catalytic mechanism [, ]. The first histidine is located in the N-terminal section and forms a phosphohistidine intermediate while the second is located in the C-terminal section and possibly acts as proton donor. Enzymes belonging to this family are called 'histidine acid phosphatases' and include:Escherichia colipH 2.5 acid phosphatase (gene appA).E. coli glucose-1-phosphatase () (gene agp).Yeast constitutive and repressible acid phosphatases (genes PHO3 and PHO5).Schizosaccharomyces pombeacid phosphatase (gene pho1).Aspergillus awamoriphytases A and B () (gene phyA and phyB).Mammalian lysosomal and prostatic acid phosphatase.Several Caenorhabditis eleganshypothetical proteins. | Short Name: | His_Pase_superF_clade-2 |
