Purification and properties of phosphoribosyl pyrophosphate synthetase from rat liver
Phosphoribosyl pyrophosphate synthetase has been purified extensively from rat liver. Gel filtration studies indicate that the enzyme is a complex of large molecular weight. On electron microscopy, stacking of enzyme molecules into long, linear aggregates is observed. The subunit molecular weight is 40,500, as measured by disc gel electrophoresis in sodium dodecyl sulfate. MgATP appears to be the required form of ATP as substrate, and excess free Mg/sup 2 +/ stimulates the reaction at low MgATP concentrations. The enzyme is highly specific for ribose 5-phosphate, and substrate inhibition occurs at ribose 5-phosphate concentrations above 1.5 mM. Like phosphoribosyl pyrophosphate synthetases from other sources, the rat liver enzyme requires inorganic phosphate for catalytic activity, but is not inactivated by dialysis against phosphate-free buffer. In the presence of optimal levels of phosphate and free Mg/sup 2 +/, the apparent K/sub m/ is 0.22 mM for MgATP and 0.29 mM for ribose 5-phosphate.
- Research Organization:
- Univ. of Chicago
- OSTI ID:
- 5160188
- Journal Information:
- J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 249:1; ISSN JBCHA
- Country of Publication:
- United States
- Language:
- English
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