Inhibition of orotidylate decarboxylase by 4(5H)-oxo-1-beta-D-ribofuranosylpyrazolo[3,4-d] pyrimidine-3-thiocarboxamide (APR-TC) in B lymphoblasts. Activation by adenosine kinase.
The nucleoside allopurinol riboside-3-thiocarboxamide (APR-TC; 4-(5H)oxo-1-beta-D-ribofuranosylpyrazolo[3,4,d]pyrimidine-3-thioca rboxamide) demonstrates potent in vitro antiviral activity against various DNA and RNA viruses and cytostatic activity against a variety of cell lines in culture. The IC50 for APR-TC in the splenic derived B lymphoblast cell line, WI-L2, was 0.3 microM. Adenosine kinase-deficient WI-L2 cells were resistant to growth inhibition by APR-TC, indicating that adenosine kinase (EC 2.7.1.20) is responsible for phosphorylation of APR-TC to form the monophosphate derivative (APR-TC-5'P). A 4-hr incubation of cells with 50 microM APR-TC resulted in severe depletion of intracellular pyrimidine nucleotide pools and the accumulation of 3 microM APR-TC-5'P. The cytotoxicity of APR-TC was reversed by uridine, indicating that the active form of this compound inhibits the de novo pyrimidine biosynthetic pathway. Further, APR-TC-treated cells could not utilize the pyrimidine nucleotide precursor [6-14C]orotic acid, suggesting that the UMP synthase complex is the major cellular site of inhibition. In studies utilizing cell-free lysates of WI-L2, chemically prepared APR-TC-5'P provided potent inhibition of the orotidylate decarboxylase activity (ODCase, EC 4.1.1.23) of the UMP synthase complex. APR-TC-5'P was competitive with OMP, and a Ki value of 0.35 nM was determined.
Dee Nord
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Department of Biochemistry, Nucleic Acid Research Institute, Costa Mesa, CA 92626.
Willis
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Smee
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Riley
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Revankar
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Robins
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D000248:Adenosine Kinase / Q000172:deficiency / Q000378:metabolism*; D001402:B-Lymphocytes / Q000201:enzymology*; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D009711:Nucleotides / Q000378:metabolism; D009964:Orotidine-5'-Phosphate Decarboxylase / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D014529:Uridine / Q000494:pharmacology
D009711:Nucleotides; D010770:Phosphotransferases; D000248:Adenosine Kinase; D002262:Carboxy-Lyases; D009964:Orotidine-5'-Phosphate Decarboxylase; D014529:Uridine