(PRPP) (fos-fō'dē-rī-bō'sil pī-rō-fos'fāt) 5-phosphoribosyl 1-diphosphate; d-ribose carrying a phosphate group on ribose carbon-5 and a pyrophosphate group on ribose carbon-1; an intermediate in the formation of the pyrimidine and purine nucleotides as well as oxidized nicotinamide adenine dinucleotide.