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Herein, we describe the isolation and characterization of a cyclooxygenase (COX)-like enzyme in\n                    <jats:italic>E. histolytica<\/jats:italic>\n                    that is responsible for the biosynthesis of prostaglandin (PG)E\n                    <jats:sub>2<\/jats:sub>\n                    . PGE\n                    <jats:sub>2<\/jats:sub>\n                    produced by ameba was constitutive but highly dependent on exogenous arachidonic acid substrate. COX-like activity and the immunoreactive protein were localized to the nuclear fraction of\n                    <jats:italic>E. histolytica<\/jats:italic>\n                    . The COX-like protein (72 kDa) was microsequenced and cloned by reverse transcriptase PCR. Ameba COX showed little homology with COX-1\/2 enzymes from different species at the nucleotide and amino acid levels. Surprisingly, the arachidonate-binding domain and heme-coordinating and catalytic sites, which are conserved in other species, were absent in ameba. Ameba COX expressed in\n                    <jats:italic>Escherichia coli<\/jats:italic>\n                    demonstrated COX-like enzyme activity\n                    <jats:italic>in vitro<\/jats:italic>\n                    by converting arachidonic acid into PGE\n                    <jats:sub>2<\/jats:sub>\n                    but not into PGD\n                    <jats:sub>2<\/jats:sub>\n                    or PGF\n                    <jats:sub>2\u03b1<\/jats:sub>\n                    . COX activity was inhibited with 1 mM aspirin but not with indomethacin or COX-1\/2-specific inhibitors. Taken together, these studies reveal that\n                    <jats:italic>E. histolytica<\/jats:italic>\n                    produces PGE\n                    <jats:sub>2<\/jats:sub>\n                    , by means of a previously undescribed ancestral COX-like enzyme, which could play a major role in pathogenesis and immune evasion.\n                  <\/jats:p>","DOI":"10.1073\/pnas.1835863100","type":"journal-article","created":{"date-parts":[[2003,11,16]],"date-time":"2003-11-16T15:42:47Z","timestamp":1068997367000},"page":"13561-13566","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":60,"title":["Identification and characterization of a cyclooxygenase-like enzyme from\n                    <i>Entamoeba histolytica<\/i>"],"prefix":"10.1073","volume":"100","author":[{"given":"Indranil","family":"Dey","sequence":"first","affiliation":[{"name":"Institute of Parasitology, McGill University, Macdonald Campus, 21,111 Lakeshore Road, Ste. 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