scholarly journals The pentose phosphate pathway in rabbit liver. Studies on the metabolic sequence and quantitative role of the pentose phosphate cycle by using a system in situ

1971 ◽  
Vol 123 (5) ◽  
pp. 923-943 ◽  
Author(s):  
J. F. Williams ◽  
K. G. Rienits ◽  
P. J. Schofield ◽  
M. G. Clark
Keyword(s):  
Pentose Phosphate Pathway ◽  
Time Course ◽  
Specific Radioactivity ◽  
Glucose Production ◽  
Pentose Phosphate ◽  
Rate Of Change ◽  
Exchange Reactions ◽  
High Concentration ◽  
Pentose Phosphate Cycle ◽  
Definition Of

1. The reactions of the pentose phosphate cycle were investigated by the intraportal infusion of specifically labelled [14C]glucose or [14C]ribose into the liver of the anaesthetized rabbit. The sugars were confined in the liver by haemostasis and metabolism was allowed to proceed for periods up to 5min. Metabolism was assessed by measuring the rate of change of the specific radioactivity of CO2, the carbon atoms of glucose 6-phosphate, fructose 6-phosphate and tissue glucose. 2. The quotient oxidation of [1-14C]glucose/oxidation of [6-14C]glucose as measured by the incorporation into respiratory CO2 was greater than 1.0 during most of the time-course and increased to a maximum of 3.1 but was found to decrease markedly upon application of a glucose load. 3. The estimate of the pentose phosphate cycle from C-1/C-2 ratios generally increased during the time-course, whereas the estimate of the pentose phosphate cycle from C-3/C-2 ratios varied depending on whether the ratios were measured in glucose or hexose 6-phosphates. 4. The distribution of 14C in hexose 6-phosphate after the metabolism of [1-14C]ribose showed that 65–95% of the label was in C-1 and was concluded to have been the result of a rapidly acting transketolase exchange reaction. 5. Transaldolase exchange reactions catalysed extensive transfer of 14C from [2-14C]glucose into C-5 of the hexose 6-phosphates during the entire time-course. The high concentration of label in C-4, C-5 and C-6 of the hexose 6-phosphates was not seen in tissue glucose in spite of an unchanging rate of glucose production during the time-course. 6. It is concluded that the reaction sequences catalysed by the pentose phosphate pathway enzymes do not constitute a formal metabolic cycle in intact liver, neither do they allow the definition of a fixed stoicheiometry for the dissimilation of glucose.

scholarly journals 13C n.m.r. isotopomer and computer-simulation studies of the non-oxidative pentose phosphate pathway of human erythrocytes

1993 ◽  
Vol 296 (2) ◽  
pp. 379-387 ◽  
Author(s):  
H A Berthon ◽  
W A Bubb ◽  
P W Kuchel
Keyword(s):  
Pentose Phosphate Pathway ◽  
Time Course ◽  
Pentose Phosphate ◽  
Correlation Spectroscopy ◽  
Human Erythrocytes ◽  
Oxidative Pentose Phosphate Pathway ◽  
Double Quantum ◽  
Exchange Reactions ◽  
Cosy Spectrum ◽  
Time Course Data

13C double-quantum filtered correlation spectroscopy (DQF-COSY) provides a novel method for the detection of reactions involving carbon-bond scissions. We report the use of this technique to investigate isotopic exchange reactions of the non-oxidative pentose phosphate pathway in human erythrocytes. These exchange reactions resulted in the formation of a range of isotopic isomers (isotopomers) of glucose 6-phosphate after incubation of a mixture of universally 13C-labelled and unlabelled glucose 6-phosphate with fructose 1,6-bisphosphate and haemolysates. These isotopomers were detected in the coupling patterns of cross-peaks within the DQF-COSY spectrum of the deproteinized sample. A computer model which fully describes the reactions of the non-oxidative pentose phosphate pathway in human erythrocytes has previously been constructed and tested with 31P n.m.r. time-course data in our laboratory. This model was refined using 13C n.m.r. time-course data and extended to include the range of isotopomers which may be formed experimentally by the reactions of the non-oxidative pentose phosphate pathway. The isotopomer ratios obtained experimentally from the DQF-COSY spectrum were consistent with simulations generated by this model.

Enzymes of glutamine metabolism in inflammation associated with skeletal muscle hypertrophy

1989 ◽  
Vol 257 (6) ◽  
pp. E885-E894 ◽  
Author(s):  
T. B. Kelso ◽  
C. R. Shear ◽  
S. R. Max
Keyword(s):  
Skeletal Muscle ◽  
Connective Tissue ◽  
Glutamine Synthetase ◽  
Pentose Phosphate Pathway ◽  
Tissue Repair ◽  
Time Course ◽  
Pentose Phosphate ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Plantaris Muscle

Glutamine synthesis and utilization were studied in the plantaris muscle after removal of its functional synergists, the soleus and gastrocnemius muscles. Rat plantaris muscle was compared with unoperated controls at 7, 14, and 30 days after synergist ablation and induction of hypertrophy. Glutamine synthetase activity increased from 6.17 +/- 1.77 to 33.92 +/- 2.23 nmol.h-1.mg protein-1, and glutaminase activities increased from 98.63 +/- 23.05 to 478.70 +/- 64.17 nmol.h-1.mg protein-1 7 days after surgery and remained elevated at 14 and 30 days. Sham-operated controls examined 7 days after surgery did not exhibit significantly increased glutamine synthetase activity. Histological examination revealed a large proliferation of connective tissue cells, as well as cells involved in tissue repair and inflammation; this influx was maximal 1 wk after surgery. The activity of the oxidative enzymes of the pentose phosphate pathway increased from 3.08 +/- 4.31 to 20.86 +/- 1.13 nmol.min-1.mg protein-1 1 wk after surgery. The time course of changes in pentose phosphate pathway enzymes was similar to that of the increases in glutamine synthetase, glutaminase, and cellular infiltration. Increases in muscle wet weight followed a different time course than changes in glutamine synthetase, glutaminase, and pentose phosphate pathway activities. It is concluded that the initial increases in plantaris muscle weight are probably due to edema, connective tissue proliferation, and cells involved in tissue repair and inflammation. The increase in glutamine synthetase activity appears to occur in skeletal muscle, whereas the changes in glutaminase and pentose phosphate pathway activities appear to represent infiltrating inflammatory cells. Furthermore, the increase in glutamine synthetase activity may serve to support the infiltrating cells, which appear to lack substantial capacity for glutamine production. These results represent a functional relationship between skeletal muscle glutamine synthesis and utilization by cells mediating inflammation and connective tissue repair and synthesis.

scholarly journals Dual metabolomic profiling uncovers Toxoplasma manipulation of the host metabolome and the discovery of a novel parasite metabolic capability

2018 ◽  
Author(s):  
William J. Olson ◽  
David Stevenson ◽  
Daniel Amador-Noguez ◽  
Laura J. Knoll
Keyword(s):  
Pentose Phosphate Pathway ◽  
Time Course ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Pentose Phosphate ◽  
Acid Cycle ◽  
Obligate Intracellular ◽  
Host Parasite ◽  
Host Metabolism ◽  
Sedoheptulose Bisphosphatase

AbstractThe obligate intracellular parasite Toxoplasma gondii is auxotrophic for several key metabolites and must scavenge these from the host. It is unclear how Toxoplasma manipulates host metabolism for its overall growth rate and non-essential metabolites. To address this question, we measured changes in the joint host-parasite metabolome over a time course of infection. Host and parasite transcriptomes were simultaneously generated to determine potential changes in metabolic enzyme levels. Toxoplasma infection increased activity in multiple metabolic pathways, including the tricarboxylic acid cycle, the pentose phosphate pathway, glycolysis, amino acid synthesis, and nucleotide metabolism. Our analysis indicated that changes in some pathways, such as the tricarboxylic acid cycle, derive from the parasite, while changes in others, like the pentose phosphate pathway, were host and parasite driven. Further experiments led to the discovery of a Toxoplasma enzyme, sedoheptulose bisphosphatase, which funnels carbon from glycolysis into ribose synthesis through a energetically driven dephosphorylation reaction. This second route for ribose synthesis resolves a conflict between the Toxoplasma tricarboxylic acid cycle and pentose phosphate pathway, which are both NADP+ dependent. During periods of high energetic and ribose need, the competition for NADP+ could result in lethal redox imbalances. Sedoheptulose bisphosphatase represents a novel step in Toxoplasma central carbon metabolism that allows Toxoplasma to satisfy its ribose demand without using NADP+. Sedoheptulose bisphosphatase is not present in humans, highlighting its potential as a drug target.Author SummaryThe obligate intracellular parasite Toxoplasma is commonly found among human populations worldwide and poses severe health risks to fetuses and individuals with AIDS. While some treatments are available they are limited in scope. A possible target for new therapies is Toxoplasma’s limited metabolism, which makes it heavily reliant in its host. In this study, we generated a joint host/parasite metabolome to better understand host manipulation by the parasite and to discover unique aspects of Toxoplasma metabolism that could serve as the next generation of drug targets. Metabolomic analysis of Toxoplasma during an infection time course found broad activation of host metabolism by the parasite in both energetic and biosynthetic pathways. We discovered a new Toxoplasma enzyme, sedoheptulose bisphosphatase, which redirects carbon from glycolysis into ribose synthesis. Humans lack sedoheptulose bisphosphatase, making it a potential drug target. The wholesale remodeling of host metabolism for optimal parasite growth is also of interest, although the mechanisms behind this host manipulation must be further studied before therapeutic targets can be identified.

scholarly journals A system for the study in situ of the pentose phosphate pathway in rabbit liver

1971 ◽  
Vol 123 (5) ◽  
pp. 915-922 ◽  
Author(s):  
J. F. Williams ◽  
K. G. Rienits ◽  
M. G. Clark
Keyword(s):  
Pentose Phosphate Pathway ◽  
Adenine Nucleotide ◽  
Glucose Production ◽  
Systemic Circulation ◽  
Pentose Phosphate ◽  
Rabbit Liver ◽  
Homogeneous Distribution ◽  
Body Tissues ◽  
Minute Interval

A surgical procedure for the isolation of the liver from the systemic circulation of the anaesthetized rabbit is described. The technique allowed the metabolism in situ of intraportally infused substrates to be followed for periods up to 5min, free from the contaminating influences of metabolism by other body tissues. Details of the procedures necessary to achieve the uniform infusion, homogeneous distribution and containment of 14C-labelled glucose substrates in the liver by haemostasis are described. Changes in pO2, pCO2, pH and the concentrations of NADP+, NADPH and glucose during each minute interval of the total 5min period of metabolism are given. Reactant ratios of the lactate dehydrogenase system and the adenine nucleotide system have been calculated from the concentrations of the pertinent metabolites for the same period of metabolism. Glucose production by rabbit liver in situ proceeded at the rate of 1.08μmol/min per g wet wt. of liver during the 5min metabolic interval. The presence of the oxidative reactions of the pentose phosphate pathway of glucose metabolism was inferred from the quotient oxidation of [1-14C]glucose/oxidation of [6-14C]glucose=1.8.

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 Further evidence for the classical pentose phosphate cycle in the liver

1982 ◽  
Vol 208 (3) ◽  
pp. 851-855 ◽  
Author(s):  
Robert Rognstad ◽  
Pat Wals ◽  
Joseph Katz
Keyword(s):  
Specific Radioactivity ◽  
Rat Hepatocytes ◽  
Total Radioactivity ◽  
Pentose Phosphate ◽  
Classical Type ◽  
Isolated Rat Hepatocytes ◽  
Pentose Phosphate Cycle ◽  
Fructose 1,6 Bisphosphatase ◽  
Phenazine Methosulphate ◽  
Substrate Concentrations

Isolated rat hepatocytes were incubated with [3-14C]xylitol or d-[3-14C]xylulose plus xylitol or glucose at substrate concentrations. The glucose formed was isolated and degraded to give the relative specific radioactivities in each carbon atom. C-4 of glucose had the highest specific radioactivity, followed by C-3, with half to one-fifth that of C-4. Only about 1% of the total radioactivity was in C-1. The data are compared with the predictions of the classical pentose phosphate cycle [Horecker, Gibbs, Klenow & Smyrniotis (1954) J. Biol. Chem.207, 393–403], and the proposed new version of the pentose phosphate cycle in liver [Longenecker & Williams (1980) Biochem. J.188, 847–857], which they denoted as the ‘L-type pentose cycle’. The Williams pathway predicts that the specific radioactivity of C-1 of glucose should be half that of C-4 (after correction for approximately equal labelling on C-3 and C-4 of hexose phosphate in the pathway involving fructose 1,6-bisphosphatase). The actual labelling in C-1 is 20–350-fold less than this. When the hepatocytes are incubated with phenazine methosulphate, to stimulate the oxidative branch of the pentose phosphate cycle, the predicted relationship between (C-2/C-3) and (C-1/C-3) ratios of specific radio-activities is nearly exactly in accord with the classical pentose phosphate cycle. Glucose and glucose 6-phosphate were isolated and degraded from an incubation of hepatocytes from starved/re-fed rats with [3-14C]xylitol. Although the patterns were of the classical type, there was more randomization of 14C into C-2 and C-1 in the glucose 6-phosphate isolated at the end of the incubation than in the glucose which was continuously produced.

scholarly journals Systematic Identification of Regulators of Oxidative Stress Reveals Non-canonical Roles for Peroxisomal Import and the Pentose Phosphate Pathway

Cell Reports ◽  
2020 ◽  
Vol 30 (5) ◽  
pp. 1417-1433.e7 ◽  
Author(s):  
Michael M. Dubreuil ◽  
David W. Morgens ◽  
Kanji Okumoto ◽  
Masanori Honsho ◽  
Kévin Contrepois ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Pentose Phosphate Pathway ◽  
Pentose Phosphate ◽  
Systematic Identification

scholarly journals Geranylgeranylacetone attenuates cerebral ischemia–reperfusion injury in rats through the augmentation of HSP 27 phosphorylation: a preliminary study

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Kazuya Matsuo ◽  
Kohkichi Hosoda ◽  
Jun Tanaka ◽  
Yusuke Yamamoto ◽  
Taichiro Imahori ◽  
...  
Keyword(s):  
Cerebral Ischemia ◽  
Reperfusion Injury ◽  
Pentose Phosphate Pathway ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Pentose Phosphate ◽  
Cerebral Ischemia Reperfusion ◽  
Hsp27 Phosphorylation ◽  
Cerebral Ischemia Reperfusion Injury ◽  
Preliminary Study

Abstract Background We previously reported that heat shock protein 27 (HSP27) phosphorylation plays an important role in the activation of glucose-6-phosphate dehydrogenase (G6PD), resulting in the upregulation of the pentose phosphate pathway and antioxidant effects against cerebral ischemia–reperfusion injury. The present study investigated the effect of geranylgeranylacetone, an inducer of HSP27, on ischemia–reperfusion injury in male rats as a preliminary study to see if further research of the effects of geranylgeranylacetone on the ischemic stroke was warranted. Methods In all experiments, male Wistar rats were used. First, we conducted pathway activity profiling based on a gas chromatography–mass spectrometry to identify ischemia–reperfusion-related metabolic pathways. Next, we investigated the effects of geranylgeranylacetone on the pentose phosphate pathway and ischemia–reperfusion injury by real-time polymerase chain reaction (RT-PCR), immunoblotting, and G6PD activity, protein carbonylation and infarct volume analysis. Geranylgeranylacetone or vehicle was injected intracerebroventricularly 3 h prior to middle cerebral artery occlusion or sham operation. Results Pathway activity profiling demonstrated that changes in the metabolic state depended on reperfusion time and that the pentose phosphate pathway and taurine-hypotaurine metabolism pathway were the most strongly related to reperfusion among 137 metabolic pathways. RT-PCR demonstrated that geranylgeranylacetone did not significantly affect the increase in HSP27 transcript levels after ischemia–reperfusion. Immunoblotting showed that geranylgeranylacetone did not significantly affect the elevation of HSP27 protein levels. However, geranylgeranylacetone significantly increase the elevation of phosphorylation of HSP27 after ischemia–reperfusion. In addition, geranylgeranylacetone significantly affected the increase in G6PD activity, and reduced the increase in protein carbonylation after ischemia–reperfusion. Accordingly, geranylgeranylacetone significantly reduced the infarct size (median 31.3% vs 19.9%, p = 0.0013). Conclusions As a preliminary study, these findings suggest that geranylgeranylacetone may be a promising agent for the treatment of ischemic stroke and would be worthy of further study. Further studies are required to clearly delineate the mechanism of geranylgeranylacetone-induced HSP27 phosphorylation in antioxidant effects, which may guide the development of new approaches for minimizing the impact of cerebral ischemia–reperfusion injury.

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