PHPT1 is an EDTA-insensitive phosphohistidine phosphatase that catalyzes the dephosphorylation of phosphopeptide I. Protein histidine phosphorylation and dephosphorylation in eukaryotes has been sparsely studied compared to protein serine/threonine and tyrosine phosphorylation, although protein histidine phosphorylation is estimated to account for about 6% of total protein phosphorylation in eukaryotes. Ek et al. (2002) detected no activity of PHPT1 towards phosphoserine, phosphothreonine, or phosphotyrosine peptides.
