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Pyrimidine Salvage Pathways In Toxoplasma Gondii
Author(s) -
ILTZSCH MAX H.
Publication year - 1993
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.1993.tb04877.x
Subject(s) - nucleotide salvage , cytidine , uridine , deoxyuridine , cytidine deaminase , biochemistry , uracil , deoxycytidine , biology , pyrimidine , thymidine , chemistry , enzyme , nucleotide , dna , rna , genetics , chemotherapy , gemcitabine , gene
. Pyrimidine salvage enzyme activities in cell‐free extracts of Toxoplasma gondii were assayed in order to determine which of these enzyme activities are present in these parasites. Enzyme activities that were detected included phosphoribosyltransferase activity towards uracil (but not cytosine or thymine), nucleoside phosphorylase activity towards uridine, deoxyuridine and thymidine (but not cytidine or deoxycytidine), deaminase activity towards cytidine and deoxycytidine (but not cytosine, cytidine 5′‐monophosphate or deoxycytidine 5′‐monophosphate), and nucleoside 5′‐monophosphate phosphohydrolase activity towards all nucleotides tested. No nucleoside kinase or phosphotransferase activity was detected, indicating that T. gondii lack the ability to directly phosphorylate nucleosides. Toxoplasma gondii appear to have a single non‐specific uridine phosphorylase enzyme which can catalyze the reversible phosphorolysis of uridine, deoxyuridine and thymidine, and a single cytidine deaminase activity which can deaminate both cytidine and deoxycytidine. These results indicate that pyrimidine salvage in T. gondii probably occurs via the following reactions: cytidine and deoxycytidine are deaminated by cytidine deaminase to uridine and deoxyuridine, respectively; uridine and deoxyuridine are cleaved to uracil by uridine phosphorylase; and uracil is metabolized to uridine 5′‐monophosphate by uracil phosphoribosyltransferase. Thus, uridine 5′‐monophosphate is the end‐product of both de novo pyrimidine biosynthesis and pyrimidine salvage in T. gondii.