Oxygen-18 studies on the oxidative and nonoxidative pentose phosphate pathways in wild-type and mutant Escherichia coli cells

Johnson, Richard D.; Krasna, Alvin I.; Rittenberg, D.

doi:10.1021/bi00734a021

Cited by 15 publications

(10 citation statements)

References 18 publications

(20 reference statements)

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“…Like the single-gene mutants in the oxidative branch, they do not require ribose supplementation, although double mutants, gnd tkt, do (168). Thus, the mutants demonstrate that either the ' oxidative or the nonoxidative route is adequate for ribose synthesis, as confirmed by labeling (1,168,169). The only other reaction with reported mutants is ribose-phosphate isomerase.…”

Section: Pentose-phosphate Pathwaymentioning

confidence: 63%

“…Flux determination in the pentose-phosphate pathway of E. coli is not understood. Labeling experiments (168,169,172) suggest reduced use of the oxidative branch anaerobically, pgi mutants do not grow anaerobically on glucose (nor edd mutants on gluconate), and limitation in NADPH reoxidation may be an explanation. The idea that flux might be limited in the same way aerobically was not supported by a study of pyridine nucleotide levels in wild-type and in a mutant with elevated glucose-6-P dehydrogenase (173); also, loss of transhydrogenase made no difference to growth of a pgi mutant on glucose (174).…”

Section: Pentose-phosphate Pathwaymentioning

confidence: 99%

See 1 more Smart Citation

Mutants in Glucose Metabolism

Fraenkel¹

1986

Annu. Rev. Biochem.

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Section: Pentose-phosphate Pathwaymentioning

confidence: 63%

Section: Pentose-phosphate Pathwaymentioning

confidence: 99%

Mutants in Glucose Metabolism

Fraenkel¹

1986

Annu. Rev. Biochem.

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“…The synthesis of PRPP from adenosine 5'-triphosphate and ribose 5-phosphate is considered to be regulated by the availability ofribose 5-phosphate (12). It has also been shown that glucose 6-phosphate dehydrogenase activity is the key enzyme in hexose monophosphate shunt functioning, through which ribose 5-phosphate is channeled (12). It is interesting to consider whether the differences in supply of PRPP found here represent biochemical differences in hexose monophosphate shunt in the cell types.…”

mentioning

confidence: 81%

“…Although there are some reports on the supply of PRPP in erythrocytes, there is no information regarding the supply of PRPP in human leukemic leukocytes and L1210 cells. The synthesis of PRPP from adenosine 5'-triphosphate and ribose 5-phosphate is considered to be regulated by the availability ofribose 5-phosphate (12). It has also been shown that glucose 6-phosphate dehydrogenase activity is the key enzyme in hexose monophosphate shunt functioning, through which ribose 5-phosphate is channeled (12).…”

mentioning

confidence: 99%

Comparative Study of 6-Mercaptopurine Metabolism in Human Leukemic Leukocytes and L1210 Cells

Higuchi¹,

Nakamura

Uchino

et al. 1977

Antimicrob Agents Chemother

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Leukocytes from patients with leukemia and L1210 cells from mice were examined for the rate offormation and cellular concentration of phosphoribosylpyrophosphate, the rate of thioinosinic acid formation, and a number of selected enzymes involved in purine nucleotide synthesis. The amount of thioinosinic acid formed in L1210 cells was much higher than that in human leukemic leukocytes. In cell extracts, the synthesis of thioinosinic acid was similar in both cell types, and the amount of purine phosphoribosyltransferase was not rate limiting in either case. Much higher concentrations and rates of formation of phosphoribosylpyrophosphate were found in L1210 cells than in human leukemic leukocytes. The difference in response to 6-mercaptopurine between L1210 cells and human leukemic leukocytes might be attributed to their difference in supply of phosphoribosylpyrophosphate. Phosphoribosylpyrophosphate-amidotransferase was found to be high in L1210 cells, but was not detected in human leukemic leukocytes.The enzymes responsible for purine nucleotide synthesis have been only partially studied in L1210 cells (4,26). Few studies have been done on the characterization of the enzymes that are essential to the mechanism of action of 6-mercaptopurine (6-MP) in humans (5,19,20). It is well known that nucleotides can be formed by means of a de novo pathway from single metabolites or, alternatively, synthesized from preformed purine bases by means of salvage pathways. Synthesis ofpurine nucleotides from preformed purines in cells has been shown to be controlled more extensively by the endogenous supply of phosphoribosylpyrophosphate (PRPP) than by the activity of the purine phosphoribosyltransferase in experimental animal tumor cells (7), human erythrocytes (24), and lymphoblasts (6). To study the regulation of purine nucleotide synthesis and to clarify the mechanism of action of 6-MP in humans, we have undertaken comparative studies on the salvage and de novo pathways, the cellular concentration of PRPP, and the enzymes responsible for PRPP formation in human leukemic leukocytes and L1210 cells. been given 6-MP during the preceding month. Blood was drawn by venipuncture into heparinized tubes. The plasma and buffy coat were separated by centrifugation in the cold and then removed. Sedimented erythrocytes were washed twice with cold, 0.9% NaCl solution.Isolation of leukocytes. Leukocytes were isolated from peripheral blood by the dextran sedimentation procedure (23). The cells were mixed with 1 volume of 3% dextran in 0.9% NaCl solution and allowed to sediment at room temperature for 30 to 45 min until a good separation was noted. The supernatant containing leukocytes, platelets, and some erythrocytes was decanted into a test tube in which all subsequent steps were performed. The cells were sedimented at 500 x g for 10 min, washed with 0.9% NaCl solution, and sedimented at 500 x g for 10 min. The cells were suspended in 0.9% NaCl solution and sedimented as described above. The leukocyte pellet was suspended in 1 ml of 0.9% N...

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“…Glucose-6-phosphate dehydrogenase plays a key role in the oxidative branch of the pentose phosphate pathway. In E. coli, this pathway is the route through which an estimated lOY'&-30% of total utilized glucose is metabolized (Cohen 195 1;Wang et al 1958;Model and Rittenberg 1967); it accounts for approximately 50% of the total ribose produced by the cells (Johnson et al 1973); and it is generally agreed to be an important source of reducing power (Katz and Rognstad 1967). Although the enzymes of the pathway, including G6PD, are produced constitutively in E. coli (Fraenkel and Levisohn 1967;Fraenkel 1968;Fraenkel and Banetjee 1971), little is known about the overall regulation of the pathway other than that it is indeed regulated, most likely at the level of G6PD itself (Orthner and Pizer 1974).…”

Section: Introductionmentioning

confidence: 99%

Selective neutrality of glucose-6-phosphate dehydrogenase allozymes in Escherichia coli.

Dykhuizen

Framond²,

Hartl³

1984

Molecular Biology and Evolution

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Six naturally occurring alleles representing four electromorphs of the enzyme glucose-6-phosphate dehydrogenase were transferred by Pl-mediated transduction from natural isolates of Escherichia coli into the genetic background of E. coli K12 and were studied in pairwise competition in chemostats limited for glucose in order to estimate differences in growth rate associated with the alleles. Although the level of resolution of such experiments is a growth rate differential of approximately 0.002 h-l, no significant differences among the strains were found. Studies of apparent K, and V,,, in crude enzyme extracts of the strains also failed to reveal any significant differences among the electromorphs.These results support the view that the alleles are selectively neutral or nearly neutral under these conditions.

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Oxygen-18 studies on the oxidative and nonoxidative pentose phosphate pathways in wild-type and mutant Escherichia coli cells

Cited by 15 publications

References 18 publications

Mutants in Glucose Metabolism

Mutants in Glucose Metabolism

Comparative Study of 6-Mercaptopurine Metabolism in Human Leukemic Leukocytes and L1210 Cells

Selective neutrality of glucose-6-phosphate dehydrogenase allozymes in Escherichia coli.

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