Abstract
The supply of ribose for nucleotide synthesis is considered a major function of the oxidative pentose shunt (PS). We have evaluated this function on the basis of ribose-5-phosphate (R5P) and PRPP concentration and generation in normal and G6PD-deficient fibroblasts. PS in normal cells accounts for 0.8% of glucose utilization. It can be stimulated over 10-fold by methylene blue (MB) and inhibited 85% by 6-aminonicotinamide (AN) without affecting PRPP levels or generation. PS in mutant cells is 30% lower than normal and barely affected by MB or AN. Basal R5P, PRPP, and inorganic phosphate (Pi) levels are somewhat higher in mutant cells, and MB elevates PRPP. Addition of AN plus MB depletes Pi, PRPP and adenine nucleotides in normal cells, but in the mutant R5P and PRPP rise and nucleotides remain unaltered. We conclude that oxidative PS is not essential for R5P generation: hence G6PD-deficient cells have no defect in PRPP or nucleotide synthesis. They are also protected from the combined effect of AN and MB, which is based on Pi depletion in normal fibroblasts. Pi is the prime modulator of PRPP synthetase in vivo.
Supported by the Academy of Finland, NIH (18197), the Kroc Foundation, and V.A. Medical Research Service.
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Raivio, K., Krumholz, H., Lazar, C. et al. 5-phosphoribosyl-l-pyrophiosphate (PRPP) synthesis in glucose-6-phosphate dehydrogenase (G6PD) deficiancy: 78. Pediatr Res 14, 177–178 (1980). https://doi.org/10.1203/00006450-198002000-00105
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DOI: https://doi.org/10.1203/00006450-198002000-00105