TY - JOUR
T1 - Phosphoribosylpyrophosphate synthetase of Escherichia coli, Identification of a mutant enzyme
AU - Hove-Jensen, Bjarne
AU - Nygaard, Per
PY - 1982/8
Y1 - 1982/8
N2 - From an Escherichia coli purine auxotroph a mutant defective in phosphoribosylpyrophosphate (PRib‐PP) synthetase has been isolated and partially characterized. In contrast to the parental strain, the mutant was able to grow on nucleosides as purine source, whereas growth on purine bases was reduced. Kinetic analysis of the mutant PRib‐PP synthetase revealed an apparent K m for ATP and ribose 5‐phosphate of 1.0 mM and 240 μM respectively, compared to 60 μM and 45 μM respectively for the wild‐type enzyme. ADP, which inhibits the wild‐type enzyme at a concentration of 0.5 mM ribose 5‐phosphate, stimulated the mutant enzyme. The activity of PRib‐PP synthetase in crude extract was higher in the mutant than in the parent. When starved for purines an accumulation of PRib‐PP was observed in the parent strain, while the pool decreased in the mutant. During pyrimidine starvation derepression of PRib‐PP synthetase activity was observed in both strains, although to a lesser extent in the mutant. Our data suggest that the mutant harbors a mutation in the structural gene for PRib‐PP synthetase. The mutation responsible for the altered PRib‐PP synthetase was located in the purB‐hemA region at 26 min on the recalibrated linkage map.
AB - From an Escherichia coli purine auxotroph a mutant defective in phosphoribosylpyrophosphate (PRib‐PP) synthetase has been isolated and partially characterized. In contrast to the parental strain, the mutant was able to grow on nucleosides as purine source, whereas growth on purine bases was reduced. Kinetic analysis of the mutant PRib‐PP synthetase revealed an apparent K m for ATP and ribose 5‐phosphate of 1.0 mM and 240 μM respectively, compared to 60 μM and 45 μM respectively for the wild‐type enzyme. ADP, which inhibits the wild‐type enzyme at a concentration of 0.5 mM ribose 5‐phosphate, stimulated the mutant enzyme. The activity of PRib‐PP synthetase in crude extract was higher in the mutant than in the parent. When starved for purines an accumulation of PRib‐PP was observed in the parent strain, while the pool decreased in the mutant. During pyrimidine starvation derepression of PRib‐PP synthetase activity was observed in both strains, although to a lesser extent in the mutant. Our data suggest that the mutant harbors a mutation in the structural gene for PRib‐PP synthetase. The mutation responsible for the altered PRib‐PP synthetase was located in the purB‐hemA region at 26 min on the recalibrated linkage map.
UR - http://www.scopus.com/inward/record.url?scp=0020447640&partnerID=8YFLogxK
U2 - 10.1111/j.1432-1033.1982.tb06782.x
DO - 10.1111/j.1432-1033.1982.tb06782.x
M3 - Journal article
SN - 0014-2956
VL - 126
SP - 327
EP - 332
JO - European Journal of Biochemistry
JF - European Journal of Biochemistry
IS - 2
ER -