Nudix Hydrolases That Degrade Dinucleoside and Diphosphoinositol Polyphosphates Also Have 5-Phosphoribosyl 1-Pyrophosphate (PRPP) Pyrophosphatase Activity That Generates the Glycolytic Activator Ribose 1,5-Bisphosphate

• Published in: The Journal of biological chemistry 2002-12, Vol.277 (49), p.47313-47317
• Main Authors: Fisher, David I., Safrany, Stephen T., Strike, Peter, McLennan, Alexander G., Cartwright, Jared L.
• Format: Article
• Language: English
• Subjects: Binding Sites; Caenorhabditis elegans; Chromatography, High Pressure Liquid; Chromatography, Ion Exchange; Deinococcus - enzymology; Deinococcus radiodurans; Glycolysis; Humans; Hydrolysis; Kinetics; Models, Molecular; Mutation; Pentosephosphates - chemistry; Protein Binding; Recombinant Proteins - metabolism; Substrate Specificity; Time Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M209795200

A total of 17 Nudix hydrolases were tested for their ability to hydrolyze 5-phosphoribosyl 1-pyrophosphate (PRPP). All 11 enzymes that were active toward dinucleoside polyphosphates with 4 or more phosphate groups as substrates were also able to hydrolyze PRPP, whereas the 6 that could not and that have coenzyme A, NDP-sugars, or pyridine nucleotides as preferred substrates did not degrade PRPP. The products of hydrolysis were ribose 1,5-bisphosphate and Pi. Active PRPP pyrophosphatases included the diphosphoinositol polyphosphate phosphohydrolase (DIPP) subfamily of Nudix hydrolases, which also degrade the non-nucleotide diphosphoinositol polyphosphates. Km andkcat values for PRPP hydrolysis for theDeinococcus radiodurans DR2356 (di)nucleoside polyphosphate hydrolase, the human diadenosine tetraphosphate hydrolase, and human DIPP-1 (diadenosine hexaphosphate and diphosphoinositol polyphosphate hydrolase) were 1 mm and 1.5 s−1, 0.13 mm and 0.057 s−1, and 0.38 mm and 1.0 s−1, respectively. Active site mutants of theCaenorhabditis elegans diadenosine tetraphosphate hydrolase had no activity, confirming that the same active site is responsible for nucleotide and PRPP hydrolysis. Comparison of the specificity constants for nucleotide, diphosphoinositol polyphosphate, and PRPP hydrolysis suggests that PRPP is a significant substrate for theD. radiodurans DR2356 enzyme and for the DIPP subfamily. In the latter case, generation of the glycolytic activator ribose 1,5-bisphosphate may be a new function for these enzymes.