Purification and properties of phosphoribosyl-diphosphate synthetase from Bacillus subtilis.
Phosphoribosyl-diphosphate (PPRibP) synthetase from Bacillus subtiliis has been purified to near homogeneity from an Escherichia coli delta prs strain bearing the cloned B. subtilis prs gene, encoding PPRibP synthentase, on a plasmid. The Mr of the subunit (34,000) and its amino-terminal amino acid sequence (14 residues) were in complete agreement with expectations from the nucleotide sequence of the prs gene. The Mr of the native enzyme (280,000 +/- 10,000) was consistent with an octameric quaternary structure. No tendency toward multiple states of aggregation of the enzyme was seen. The purified enzyme required Mg2+ and inorganic phosphate for activity; Mn2+ supported only 30% the activity seen with Mg2+. Michaelis constants for ATP and ribose 5-phosphate (Rib5P) were 0.66 mM and 0.48 mM, respectively. Of several end products tested, only ADP was strongly inhibitory; GDP was a weak inhibitor. ADP inhibition displayed homotropic cooperativity and was enhanced by increasing saturation of the enzyme with ATP. These observations strongly suggest a specific allosteric site for ADP binding. A comparison of physical and kinetic properties of bacterial and mammalian PPRibP synthetases is presented.
Arnvig
K
K
Enzyme Division, Institute of Biological Chemistry B, University of Copenhagen, Denmark.
Hove-Jensen
B
B
Switzer
R L
RL
D000244:Adenosine Diphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010770:Phosphotransferases / Q000302:isolation & purification*; D012268:Ribose-Phosphate Pyrophosphokinase / Q000302:isolation & purification* / Q000378:metabolism
D001426:Bacterial Proteins; D000244:Adenosine Diphosphate; D010770:Phosphotransferases; D012268:Ribose-Phosphate Pyrophosphokinase