We have found that the anaerobic protozoan parasite Giardia lamblia is incapable of de novo pyrimidine metabolism, as shown by its inability to incorporate orotate, bicarbonate, and aspartate into the pyrimidine nucleotide pool. Results from high performance liquid chromatography of pyrimidine and pyrimidine nucleoside pulse-labeled nucleotide pools and enzyme assays suggest that the parasite satisfies its pyrimidine nucleotide needs predominantly through salvage of uracil by a cytoplasmic uracil phosphoribosyltransferase. Exogenous uridine and cytidine are primarily converted to uracil by the action of uridine hydrolase and cytidine deaminase before incorporation into nucleotide pools. Direct salvage of cytosine occurs to a relatively limited extent via cytosine phosphoribosyltransferase. G. lamblia relies on salvage of exogenous thymidine for ribosylthymine monophosphate (TMP) synthesis, accomplished primarily through the action of a 100,000 g-pelletable thymidine phosphotransferase.
Article| March 01 1985
Pyrimidine salvage in Giardia lamblia.
S M Aldritt
C C Wang
Online ISSN: 1540-9538
Print ISSN: 0022-1007
J Exp Med (1985) 161 (3): 437–445.
S M Aldritt, P Tien, C C Wang; Pyrimidine salvage in Giardia lamblia.. J Exp Med 1 March 1985; 161 (3): 437–445. doi: https://doi.org/10.1084/jem.161.3.437
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