title: The enzymes of pyrimidine biosynthesis in a range of parasitic protozoa and helminths.
abstract: The activities of carbamoylphosphate synthase, aspartate transcarbamoylase, dihydroorotase, orotate phosphoribosyl transferase and orotidine-5'-phosphate decarboxylase, five of the six enzymes of pyrimidine biosynthesis, have been measured in Crithidia fasciculata, Trypanosoma cruzi, Leishmania major, Trichomonas vaginalis, Eimeria tenella, Toxoplasma gondii, Plasmodium berghei, Fasciola gigantica, Schistosoma mansoni, Hymenolepis diminuta, Nippostrongylus brasiliensis and Trichuris muris. The majority of organisms contained all five enzyme activities. However, in T. vaginalis only carbamoylphosphate synthetase activity and in E. tenella only orotate phosphoribosyl transferase and orotidine-5'-phosphate decarboxylase activities could be detected. It appears therefore that the ability to synthesise pyrimidines by the de novo route is probably both common and widespread amongst parasitic organisms.
mesh_terms: D000818:Animals; D016782:Apicomplexa / Q000201:enzymology*; D001221:Aspartate Carbamoyltransferase / Q000378:metabolism; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000378:metabolism; D004080:Dihydroorotase / Q000378:metabolism; D056890:Eukaryota / Q000201:enzymology*; D009348:Nematoda / Q000201:enzymology*; D009962:Orotate Phosphoribosyltransferase / Q000378:metabolism; D009964:Orotidine-5'-Phosphate Decarboxylase / Q000378:metabolism; D010986:Platyhelminths / Q000201:enzymology*; D011743:Pyrimidines / Q000096:biosynthesis*
chemical_list: D011743:Pyrimidines; D001221:Aspartate Carbamoyltransferase; D009962:Orotate Phosphoribosyltransferase; D004080:Dihydroorotase; D009964:Orotidine-5'-Phosphate Decarboxylase; D002222:Carbamoyl-Phosphate Synthase (Ammonia)