5-Phosphoribosyl-1-pyrophosphate (PRPP) is an essential substrate for biosynthesis of nucleotides, tryptophan and histidine, functioning as
the phosphoribosyl donor. PRPP is synthesised from ribose-5-phosphate and ATP by PRPP synthetase (ribose phosphate
pyrophosphokinase, EC 2.7.6.1). In the present review, the occurrence and biosynthesis of PRPP in plant cells and tissues are summarized,
and then the properties of two types of plant PRPP synthetases are described. In addition to the inorganic phosphate (Pi)-dependent PRPP
synthetases (class I) which have similar properties to mammalian enzymes, plant specific Pi-independent PRPP synthetases (class II) have
been discovered in plants. Finally, reports which show fluctuation of the PRPP synthetase activity accompanied by various physiological
phenomena in plants and the transgenic plants which enhanced PRPP synthetase activity and relation to biotechnology are introduced.
Key words: 5-phosphoribosyl-1pyrophosphate (PRPP), nucleotide biosynthesis, PRPP synthetase, metabolite, enzyme, plant, PRS gene
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