2-phosphoglycolate phosphatase, prokaryotic <p> This family of sequences represent 2-phosphoglycolate phosphatase which is limited to the prokaryotes. PGP is an essential enzyme in the glycolate salvage pathway in higher organisms (photorespiration in plants). Phosphoglycolate results from the oxidase activity of RubisCO in the Calvin cycle when concentrations of carbon dioxide are low relative to oxygen. In <taxon tax_id="106590">Ralstonia eutropha</taxon> and <taxon tax_id="1063">Rhodobacter sphaeroides</taxon>, the PGP gene (CbbZ) is located on an operon along with other Calvin cycle enzymes including RubisCO [<cite idref="PUB00009585"/>, <cite idref="PUB00009586"/>]. The only other pertinent experimental evidence concerns the gene from <taxon tax_id="562">Escherichia coli</taxon> [<cite idref="PUB00009587"/>]. The in vitro activity of the Ralstonia and Escherichia enzymes was determined with crude cell extracts of strains containing PGP on expression plasmids and compared to controls. In E. coli, however, there does not appear to be a functional Calvin cycle (RubisCO is absent), although the E. coli PGP gene (gph) is on the same operon (dam) with ribulose-5-phosphate-3-epimerase (rpe), a gene in the pentose-phosphate pathway (along with other, unrelated genes). The E. coli enzyme is not expressed under normal laboratory conditions; the pathway to which it belongs has not been determined. In fact, the possibility exists, although unlikely, that this enzyme, as well as others, within this equivalog have as their physiological substrate another, closely related molecule. The protein from <taxon tax_id="2371">Xylella fastidiosa</taxon> has no experimental evidence, but is a plant pathogen and thus may obtain phosphoglycolate from its host. This model has been restricted to encompass only proteobacteria as no related PGP has been verified outside of this clade. Sequences from <taxon tax_id="63363">Aquifex aeolicus</taxon> and <taxon tax_id="160">Treponema pallidum</taxon> fall between the trusted and noise cut-offs. Just below the noise cut-off is a gene which is part of the operon for the biosynthesis of the blue pigment, indigoidine, from <taxon tax_id="556">Erwinia chrysanthemi</taxon>, a plant pathogen [<cite idref="PUB00009588"/>]. It does not seem likely, considering the proposed biosynthetic mechanism, that the dephosphorylation of phosphoglycolate or a closely related compound is required. Possibly, this gene is fortuitously located in this operon, or has an indirect relationship to the necessity for the biosynthesis of this compound. This enzyme is a member of the Haloacid Dehalogenase (HAD) superfamily of aspartate-nucleophile hydrolase enzymes.</p>