scholarly journals New reaction sequences for the non-oxidative pentose phosphate pathway

1978 ◽  
Vol 176 (1) ◽  
pp. 257-282 ◽  
Author(s):  
J F Williams ◽  
P F Blackmore ◽  
M G Clark
Keyword(s):  
Volatile Compounds ◽  
Rat Liver ◽  
Pentose Phosphate Pathway ◽  
Carbon Balance ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Rat Tissues ◽  
Phosphate Metabolism ◽  
Reaction Sequence ◽  
Triose Phosphate

1. Reactions leading to the formation of 14C-labelled volatile compounds and compounds volatile under acid conditions were investigated in a system actively synthesizing hexose 6-phosphates from [U-14C]ribose 5-phosphate by reactions catalysed by enzymes prepared from acetone-dried powder of rat liver; no reactions involving 14C-labelled volatile compounds were detected. Similarly the fixation of 14C-labelled volatile compounds into hexose 6-phosphate could not be detected. 2. A complete carbon balance was made for the reactants, intermediates and products of the reactions involved in the conversion of ribose 5-phosphate into hexose 6-phosphate by enzymes of rat liver. Five additional intermediates of pentose 5-phosphate metabolism in liver were detected, namely D-manno-heptulose 7-phosphate, D-altro-heptulose 1,7-bisphosphate, D-glycero-D-ido-octulose 1,8-bisphosphate, D-glycero-D-altro-octulose 1,8-bisphosphate and D-arabinose 5-phosphate. 3. D-Arabinose 5-phosphate was found to be utilized by a rat liver enzyme preparation to produce both hexose 6-phosphate and triose phosphate. 4. D-Arabinose 5-phosphate was reversibly converted into other pentose 5-phosphates. Paper chromatographic and enzymic evidence indicated that the conversion involved an enzyme tentatively named arabinose phosphate 2-epimerase, which catalyses the following reaction: D-arabinose 5-P in equilibrium D-ribose-5-P. 5. A variety of rat tissues also utilized D-arabinose 5-phosphate to produce both hexose 6-phosphate and triose phosphate and at a rate comparable with that obtained with D-ribose 5-phosphate. 6. A new reaction sequence for the non-oxidative pentose phosphate pathway in liver is proposed.

scholarly journals Elevated activity of the oxidative and non-oxidative pentose phosphate pathway in (pre)neoplastic lesions in rat liver

2008 ◽  
Vol 89 (4) ◽  
pp. 232-240 ◽  
Author(s):  
Wilma M. Frederiks ◽  
Pedro Vizan ◽  
Klazina S. Bosch ◽  
Heleen Vreeling-Sindelárová ◽  
Joan Boren ◽  
...  
Keyword(s):  
Rat Liver ◽  
Pentose Phosphate Pathway ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Neoplastic Lesions ◽  
Elevated Activity

scholarly journals The fate of 14C in glucose 6-phosphate synthesized from [1-14C]Ribose 5-phosphate by enzymes of rat liver

1978 ◽  
Vol 176 (1) ◽  
pp. 241-256 ◽  
Author(s):  
J F Williams ◽  
M G Clark ◽  
P F Blackmore
Keyword(s):  
Rat Liver ◽  
Pentose Phosphate Pathway ◽  
Specific Radioactivity ◽  
Early Time ◽  
Pentose Phosphate ◽  
Enzyme Extract ◽  
Reaction Sequence ◽  
Time Intervals ◽  
A Value ◽  
Initial Substrate

1. Glucose 5-phosphate was synthesized from ribose 5-phosphate by an enzyme extract prepared from an acetone-dried powder of rat liver. Three rates of ribose 5-phosphate utilization were observed during incubation for 17 h. An analysis of intermediates and products formed throughout the incubation revealed that as much as 20% of the substrate carbon could not be accounted for. 2. With [1-14C]ribose 5-phosphate as substrate, the specific radioactivity of [14C]glucose 6-phosphate formed was determined at 1, 2, 5 and 30 min and 3, 8 and 17 h. It increased rapidly to 1.9-fold the initial specific radioactivity of [1-14C]ribose 5-phosphate at 3 h and then decreased to a value approximately equal to that of the substrate at 6 h, and finally at 17 h reached a value 0.8-fold that of the initial substrate [1-14C]ribose 5-phosphate. 3. The specific radioactivity of [14C]ribose 5-phosphate decreased to approx. 50% of its inital value during the first 3 h of the incubation and thereafter remained unchanged. 4. The distribution of 14C in the six carbon atoms of [14C]glucose 6-phosphate formed from [1-14C]ribose 5-phosphate at 1, 2, 5 and 30 min and 3, 8 and 17 h was determined. The early time intervals (1–30 min) were characterized by large amounts of 14C in C-2 and in C-6 and with C-1 and C-3 being unlabelled. In contrast, the later time intervals (3–17 h) were characterized by the appearance of 14C in C-1 and C-3 and decreasing amounts of 14C in C-2 and C-6. 5. It is concluded that neither the currently accepted reaction sequence for the non-oxidative pentose phosphate pathway nor the ‘defined’ pentose phosphate-cycle mechanism can be reconciled with the labelling patterns observed in glucose 6-phosphate formed during the inital 3 h of the incubation.

scholarly journals Pentose Phosphate Pathway Reactions in Photosynthesizing Cells

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1547
Author(s):  
Thomas D. Sharkey
Keyword(s):  
Pentose Phosphate Pathway ◽  
Strong Association ◽  
Pentose Phosphate ◽  
Critical Component ◽  
Reaction Sequence ◽  
Response To Stress ◽  
Labeling Pattern

The pentose phosphate pathway (PPP) is divided into an oxidative branch that makes pentose phosphates and a non-oxidative branch that consumes pentose phosphates, though the non-oxidative branch is considered reversible. A modified version of the non-oxidative branch is a critical component of the Calvin–Benson cycle that converts CO2 into sugar. The reaction sequence in the Calvin–Benson cycle is from triose phosphates to pentose phosphates, the opposite of the typical direction of the non-oxidative PPP. The photosynthetic direction is favored by replacing the transaldolase step of the normal non-oxidative PPP with a second aldolase reaction plus sedoheptulose-1,7-bisphosphatase. This can be considered an anabolic version of the non-oxidative PPP and is found in a few situations other than photosynthesis. In addition to the strong association of the non-oxidative PPP with photosynthesis metabolism, there is recent evidence that the oxidative PPP reactions are also important in photosynthesizing cells. These reactions can form a shunt around the non-oxidative PPP section of the Calvin–Benson cycle, consuming three ATP per glucose 6-phosphate consumed. A constitutive operation of this shunt occurs in the cytosol and gives rise to an unusual labeling pattern of photosynthetic metabolites while an inducible shunt in the stroma may occur in response to stress.

scholarly journals Targeting oxidative pentose phosphate pathway prevents recurrence in mutant Kras colorectal carcinomas

PLoS Biology ◽  
2019 ◽  
Vol 17 (8) ◽  
pp. e3000425 ◽  
Author(s):  
WenChao Gao ◽  
YuTing Xu ◽  
Tao Chen ◽  
ZunGuo Du ◽  
XiuJuan Liu ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Colorectal Carcinomas

Significance of the Non-Oxidative Pentose Phosphate Pathway in Aspergillus oryzae Grown on Different Carbon Sources

1991 ◽  
Vol 46 (3-4) ◽  
pp. 223-227 ◽  
Author(s):  
Maria Luisa Peleato ◽  
Teresa Muiño-Blanco ◽  
José Alvaro Cebrian Pérez ◽  
Manuel José López-Pérez
Keyword(s):  
Aspergillus Oryzae ◽  
Pentose Phosphate Pathway ◽  
Enzyme Activities ◽  
Developmental Stages ◽  
Carbon Sources ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Pentose Pathway ◽  
Hexose Phosphates

Specific enzyme activities of the non-oxidative pentose phosphate pathway in Aspergillus oryzae mycelia grown on different carbon sources were determined. Mycelia grown on glucose, mannitol and ribose show the highest specific activities, ribose 5-phosphate isomerase being specially very enhanced. Moreover, transketolase, transaldolase, ribose 5-phosphate isomerase and ribulose 5-phosphate 3-epimerase were determined in different developmental stages of mycelia grown on glucose, mannitol and ribose. The non-oxidative pentose phosphate pathway is more active during conidiogenesis, except for ribulose 5-phosphate 3-epimerase, suggesting a fundamental role of this pathway during that stage to supply pentoses for nucleic acids biosynthesis. A general decrease of the enzyme activities was found in sporulated mycelia. Arabinose 5-phosphate was tested as metabolite of the pentose pathway. This pentose phosphate was not converted into hexose phosphates or triose phosphates and inhibits significantly the ribose 5-phosphate utilization, being therefore unappropriate to support the Aspergillus oryzae growth.

scholarly journals Beneficial effects of acute inhibition of the oxidative pentose phosphate pathway in the failing heart

2014 ◽  
Vol 306 (5) ◽  
pp. H709-H717 ◽  
Author(s):  
Claudio Vimercati ◽  
Khaled Qanud ◽  
Gianfranco Mitacchione ◽  
Danuta Sosnowska ◽  
Zoltan Ungvari ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Pentose Phosphate Pathway ◽  
Tissue Concentration ◽  
Glucose Consumption ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Stroke Work ◽  
Failing Heart

In vitro studies suggested that glucose metabolism through the oxidative pentose phosphate pathway (oxPPP) can paradoxically feed superoxide-generating enzymes in failing hearts. We therefore tested the hypothesis that acute inhibition of the oxPPP reduces oxidative stress and enhances function and metabolism of the failing heart, in vivo. In 10 chronically instrumented dogs, congestive heart failure (HF) was induced by high-frequency cardiac pacing. Myocardial glucose consumption was enhanced by raising arterial glycemia to levels mimicking postprandial peaks, before and after intravenous administration of the oxPPP inhibitor 6-aminonicotinamide (80 mg/kg). Myocardial energy substrate metabolism was measured with radiolabeled glucose and oleic acid, and cardiac 8-isoprostane output was used as an index of oxidative stress. A group of five chronically instrumented, normal dogs served as control. In HF, raising glycemic levels from ∼80 to ∼170 mg/dL increased cardiac isoprostane output by approximately twofold, whereas oxPPP inhibition normalized oxidative stress and enhanced cardiac oxygen consumption, glucose oxidation, and stroke work. In normal hearts glucose infusion did not induce significant changes in cardiac oxidative stress. Myocardial tissue concentration of 6P-gluconate, an intermediate metabolite of the oxPPP, was significantly reduced by ∼50% in treated versus nontreated failing hearts, supporting the inhibitory effect of 6-aminonicotinamide. Our study indicates an important contribution of the oxPPP activity to cardiac oxidative stress in HF, which is particularly pronounced during common physiological changes such as postprandial glycemic peaks.

scholarly journals Lesions in the nuo Operon, Encoding NADH Dehydrogenase Complex I, Prevent PurF-Independent Thiamine Synthesis and Reduce Flux through the Oxidative Pentose Phosphate Pathway inSalmonella enterica Serovar Typhimurium

2000 ◽  
Vol 182 (1) ◽  
pp. 228-232 ◽  
Author(s):  
Kathy Claas ◽  
Shara Weber ◽  
Diana M. Downs
Keyword(s):  
Pentose Phosphate Pathway ◽  
Nadh Dehydrogenase ◽  
Pyridine Nucleotide ◽  
Growth Conditions ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
New Class ◽  
Nucleotide Pools ◽  
Serovar Typhimurium ◽  
Cell Data

ABSTRACT In Salmonella enterica serovar Typhimurium, PurF-independent thiamine synthesis (or alternative pyrimidine biosynthesis) allows strains, under some growth conditions, to synthesize thiamine in the absence of the first step in the purine biosynthetic pathway. Mutations have been isolated in a number of loci that prevent this synthesis and thus result in an Apb−phenotype. Here we identify a new class of mutations that prevent PurF-independent thiamine synthesis and show that they are defective in the nuo genes, which encode the major, energy-generating NADH dehydrogenase of the cell. Data presented here indicated that anuo mutant has reduced flux through the oxidative pentose phosphate pathway that may contribute to, but is not sufficient to cause, the observed thiamine requirement. We suggest that reduction of the oxidative pentose phosphate pathway capacity in a nuomutant is an attempt to restore the ratio between reduced and oxidized pyridine nucleotide pools.

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