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phosphoglycolate/pyridoxal phosphate phosphatase family 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 mammals, PGP is found in many tissues, notably in red blood cells where P-glycolate is and important activator of the hydrolysis of 2,3-bisphosphoglycerate, a major modifier of the oxygen affinity of hemoglobin. Pyridoxal phosphate (PLP, Vitamin B6) phosphatase is involved in the degradation of PLP in mammals and is widely distributed in human tissues including erythrocyes. The enzymes described here are members of the Haloacid dehalogenase superfamily of hydrolase enzymes (pfam00702). Unlike the bacterial PGP equivalog (TIGR01449), which is a member of class (subfamily) I, these enzymes are members of class (subfamily) II. These two families have almost certainly arisen from convergent evolution (although these two ancestors may themselves have diverged from a more distant HAD superfamily progenitor). The primary seed sequence for this model comes from Chlamydomonas reinhardtii, a photosynthetic alga. The enzyme has been purified and characterized and these data are fully consistent with the assignment of function as a PGPase involved in photorespiration. The second seed, from Homo sapiens chromosome 22 has been characterized as a pyridoxal phosphatase. Biochemical characterization of partially purified PGP's from various tissues including red blood cells have been performed while one gene for PGP has been localized to chromosome 16p13.3. The sequence used here maps to chromosome 22. There is indeed a related gene on chromosome 16 (and it is expressed, since EST's are found) which shows 46% identity. The chromosome 16 gene is not in evidence in nraa but translated from the genomic sequence. The third seed, from C. elegans, is only supported by sequence similarity. This model is limited to eukaryotic species including S. pombe and S. cerevisiae, although several archaea score between the trusted and noise cutoffs. This model is closely related to a family of bacterial sequences including the E. coli NagD and B. subtilus AraL genes which are characterized by the ability to hydrolyze para-nitrophenylphosphate (pNPPases or NPPases). The chlamydomonas PGPase d |
Jiyao W et al.(2023). "The conserved domain database in 2023.",