{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,28]],"date-time":"2025-10-28T14:53:10Z","timestamp":1761663190496},"reference-count":36,"publisher":"Wiley","issue":"2","license":[{"start":{"date-parts":[[2013,9,9]],"date-time":"2013-09-09T00:00:00Z","timestamp":1378684800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecular Microbiology"],"published-print":{"date-parts":[[2013,10]]},"abstract":"<jats:title>Summary<\/jats:title><jats:p>African trypanosomes are capable of both <jats:italic>de novo<\/jats:italic> synthesis and salvage of pyrimidines. The last two steps in <jats:italic>de novo<\/jats:italic> synthesis are catalysed by <jats:styled-content style=\"fixed-case\">UMP<\/jats:styled-content> synthase (<jats:styled-content style=\"fixed-case\">UMPS<\/jats:styled-content>) \u2013 a bifunctional enzyme comprising orotate phosphoribosyl transferase (<jats:styled-content style=\"fixed-case\">OPRT<\/jats:styled-content>) and orotidine monophosphate decarboxylase (<jats:styled-content style=\"fixed-case\">OMPDC<\/jats:styled-content>). To investigate the essentiality of pyrimidine biosynthesis in <jats:italic><jats:styled-content style=\"fixed-case\">T<\/jats:styled-content>rypanosoma brucei<\/jats:italic>, we generated a <jats:italic>umps<\/jats:italic> double knockout (<jats:styled-content style=\"fixed-case\">DKO<\/jats:styled-content>) line by gene replacement. The <jats:styled-content style=\"fixed-case\">DKO<\/jats:styled-content> was unable to grow in pyrimidine\u2010depleted medium <jats:italic>in vitro<\/jats:italic>, unless supplemented with uracil, uridine, deoxyuridine or <jats:styled-content style=\"fixed-case\">UMP<\/jats:styled-content>. <jats:styled-content style=\"fixed-case\">DKO<\/jats:styled-content> parasites were completely resistant to 5\u2010fluoroorotate and hypersensitive to 5\u2010fluorouracil, consistent with loss of <jats:styled-content style=\"fixed-case\">UMPS<\/jats:styled-content>, but remained sensitive to pyrazofurin indicating that, unlike mammalian cells, the primary target of pyrazofurin is not <jats:styled-content style=\"fixed-case\">OMPDC<\/jats:styled-content>. The null mutant was unable to infect mice indicating that salvage of host pyrimidines is insufficient to support growth. However, following prolonged culture <jats:italic>in vitro<\/jats:italic>, parasites regained virulence in mice despite retaining pyrimidine auxotrophy. Unlike the wild\u2010type, both pyrimidine auxotrophs secreted substantial quantities of orotate, significantly higher in the virulent <jats:styled-content style=\"fixed-case\">DKO<\/jats:styled-content> line. We propose that this may be responsible for the recovery of virulence in mice, due to host metabolism converting orotate to uridine, thereby bypassing the loss of <jats:styled-content style=\"fixed-case\">UMPS<\/jats:styled-content> in the parasite.<\/jats:p>","DOI":"10.1111\/mmi.12376","type":"journal-article","created":{"date-parts":[[2013,8,26]],"date-time":"2013-08-26T06:32:45Z","timestamp":1377498765000},"page":"443-455","source":"Crossref","is-referenced-by-count":23,"title":["<i><scp>T<\/scp>rypanosoma brucei<\/i> (<scp>UMP<\/scp> synthase null mutants) are avirulent in mice, but recover virulence upon prolonged culture <i>in vitro<\/i> while retaining pyrimidine auxotrophy"],"prefix":"10.1111","volume":"90","author":[{"given":"Han B.","family":"Ong","sequence":"first","affiliation":[{"name":"Divisional of Biological Chemistry and Drug Discovery College of Life Sciences University of Dundee  Dundee DD1\u20095EH 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