Contribution of the pentose phosphate pathway to glucose utilization by preimplantation sheep embryos

1993 ◽  
Vol 5 (3) ◽  
pp. 329 ◽  
Author(s):  
RG Wales ◽  
ZF Du
Keyword(s):  
Pentose Phosphate Pathway ◽  
Blastocyst Stage ◽  
Pentose Phosphate ◽  
Yolk Sac ◽  
Glucose Turnover ◽  
Experimental Conditions ◽  
Advanced Embryo ◽  
Total Glucose ◽  
Total Turnover ◽  
Pentose Pathway

The activity of the pentose phosphate pathway of glucose metabolism in early sheep embryos and in the structures of the advanced conceptus from Day 13 to Day 19 of pregnancy was measured quantitatively during a 2.5-h incubation with glucose as sole energy source. For embryos during cleavage, activity of this pathway accounted for 6-9% of total glucose utilized. The proportion of glucose metabolized through the pentose pathway fell progressively with development and by Day 19 represented 1-2% of glucose turnover. However, total turnover of glucose increased eight fold between the 2-cell and blastocyst stage and the amount of glucose processed through the pentose pathway increased over this time despite the fall in the proportion utilized in this way. In contrast, glucose turnover by the advanced embryo and its extra embryonic membranes progressively decreased as the structures developed. As a result, estimates of the amount of glucose utilized through the pathway per microgram dried weight per hour declined to low values at Day 19 following the peak in activity at about the time of blastulation. Trophoblast and yolk sac processed less glucose through the pentose pathway per microgram dried weight than embryonic tissue but the allantois was similar to the embryo. Overall, the pentose pathway accounted for a relatively constant proportion of the CO2 produced from glucose under these experimental conditions with values generally between 15 and 20% of total CO2 produced. When activities in the components of the advanced conceptus were expressed as the total amount of glucose processed through the pathway per hour, turnover in the embryo, allantois and yolk sac increased progressively with time. By contrast, there was a substantial trough in the activity of the trophoblast on Day 17 of pregnancy.

scholarly journals The utilization of glucose for the synthesis of milk components in the fed and starved lactating goat in vivo

1980 ◽  
Vol 186 (1) ◽  
pp. 301-308 ◽  
Author(s):  
N Chaiyabutr ◽  
A Faulkner ◽  
M Peaker
Keyword(s):  
Mammary Gland ◽  
Fatty Acid ◽  
Pentose Phosphate Pathway ◽  
Acid Synthesis ◽  
Pentose Phosphate ◽  
Glucose Turnover ◽  
Glucose Carbon ◽  
Lactating Goats ◽  
Total Glucose

1. [U-14C]Glucose and [3-3H]glucose were infused into fed and starved lactating goats in order to study glucose metabolism in the mammary gland. 2. Glucose carbon was oxidized and metabolizet to milk lactose, citrate and triacylglycerol in the lactating goat udder. 3. Recycling of glucose carbon in the lactating animal accounted for 10-20% of the total glucose turnover in the whole animal. Recycling of glucose 6-phosphate in the udder accounted for about 25% of the glucose 6-phosphate metabolized. 4. Flux of glucose 6-phosphate through the pentose phosphate pathway was sufficient to account for 34% of the NADPH required for fatty acid synthesis in the gland in the fed animal. 5. Net metabolism of glucose 6-phosphate via the pentose phosphate pathway accounted for 17.8 and 1.2% of the glucose phosphorylated by the mammary gland in the fed and starved animal respectively. Metabolism of glucose 6-phosphate via the pentose phosphate pathway was sufficient to account for all the CO2 produced from glucose in the fed animal, but only 17% of the CO2 produced from glucose in the starved animal.

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 Underestimation of the Pentose–Phosphate Pathway in Intact Primary Neurons as Revealed by Metabolic Flux Analysis

2013 ◽  
Vol 33 (12) ◽  
pp. 1843-1845 ◽  
Author(s):  
Patricia Rodriguez-Rodriguez ◽  
Emilio Fernandez ◽  
Juan P Bolaños
Keyword(s):  
Pentose Phosphate Pathway ◽  
Metabolic Flux ◽  
Pentose Phosphate ◽  
Flux Analysis ◽  
Primary Neurons ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Total Glucose ◽  
Rate Limiting ◽  
Glycolytic Rate

The rates of glucose oxidized at glycolysis and pentose–phosphate pathway (PPP) in neurons are controversial. Using [3-3H]-, [1-14C]-, and [6-14C]glucose to estimate fluxes through these pathways in resting, intact rat cortical primary neurons, we found that the rate of glucose oxidized through PPP was, apparently, ∼14% of total glucose metabolized. However, inhibition of PPP rate-limiting step, glucose-6-phosphate (G6P) dehydrogenase, increased approximately twofold the glycolytic rate; and, knockdown of phosphoglucose isomerase increased ∼1.8-fold the PPP rate. Thus, in neurons, a considerable fraction of fructose-6-phosphate returning from the PPP contributes to the G6P pool that re-enters PPP, largely underestimating its flux.

Effect of low temperatures on glucose-induced insulin secretion and glucose metabolism in isolated pancreatic islets of the rat

1990 ◽  
Vol 125 (1) ◽  
pp. 45-51 ◽  
Author(s):  
J. C. Escolar ◽  
R. Hoo-Paris ◽  
Ch. Castex ◽  
B. Ch. J. Sutter
Keyword(s):  
Insulin Secretion ◽  
Glucose Metabolism ◽  
Glucose Oxidation ◽  
Glucose Utilization ◽  
Pentose Phosphate ◽  
Experimental Conditions ◽  
Isolated Pancreatic Islets ◽  
Acid Cycle ◽  
The Difference ◽  
Pentose Pathway

ABSTRACT The direct effect of hypothermia on the inhibition of insulin secretion may result from inhibition of the availability of energetic substrates and/or the lack of metabolic signals. In order to verify this hypothesis, the insulin secretion and the main metabolic glucose pathways were measured during the incubation of rat islets. In the presence of 16·7 mmol glucose/l and at 37 °C, insulin secretion was 925 ± 119 μU/2 h per ten islets. With the same experimental conditions, glucose utilization, determined as the formation of 3H2O from [5-3H]glucose was 2225 ±184 pmol/2 h per ten islets, glucose oxidation measured as the formation of 14CO2 from [U-14C]glucose was 673 ± 51 pmol/2 h per ten islets, pentose cycle determined as the formation of 14CO2 from either [1-14C]glucose or [6-14C]glucose was 37 ± 5 pmol/2 h per ten islets; glucose oxidation by the tricarboxilic acid cycle, calculated to be the difference between glucose oxidation and pentose cycle values, was 636 pmol/2 h per ten islets. Hypothermia highly inhibited glucose-induced insulin secretion and glucose utilization. Inhibition of insulin secretion was partial at 27 °C since it was 2·5 times lower than that at 37 °C, and it was complete at 17 °C. Glucose oxidation in the tricarboxilic acid cycle was markedly inhibited by hypothermia since the inhibition coefficient (Q10) between 37 and 27 °C was 5. In contrast, glucose oxidation in the pentose phosphate shunt was enhanced at 27 °C, reaching 92 ± 17 pmol/2 h per ten islets, and it was inhibited relatively little at 17 °C. These results suggest that hypothermia markedly inhibits glucose metabolism with the exception of the pentose pathway which could play an important role by inducing the insulin secretion at 27 °C. Journal of Endocrinology (1990) 125, 45–51

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.

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 Fine tuning the glycolytic flux ratio of EP-bifido pathway for mevalonate production by enhancing glucose-6-phosphate dehydrogenase (Zwf) and CRISPRi suppressing 6-phosphofructose kinase (PfkA) in Escherichia coli

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Ying Li ◽  
He Xian ◽  
Ya Xu ◽  
Yuan Zhu ◽  
Zhijie Sun ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Conversion Rate ◽  
Metabolic Flux ◽  
Flux Ratio ◽  
Reducing Power ◽  
Pentose Phosphate ◽  
Fine Tuning ◽  
High Yield ◽  
Glycolytic Flux ◽  
Acetyl Coa

Abstract Background Natural glycolysis encounters the decarboxylation of glucose partial oxidation product pyruvate into acetyl-CoA, where one-third of the carbon is lost at CO2. We previously constructed a carbon saving pathway, EP-bifido pathway by combining Embden-Meyerhof-Parnas Pathway, Pentose Phosphate Pathway and “bifid shunt”, to generate high yield acetyl-CoA from glucose. However, the carbon conversion rate and reducing power of this pathway was not optimal, the flux ratio of EMP pathway and pentose phosphate pathway (PPP) needs to be precisely and dynamically adjusted to improve the production of mevalonate (MVA). Result Here, we finely tuned the glycolytic flux ratio in two ways. First, we enhanced PPP flux for NADPH supply by replacing the promoter of zwf on the genome with a set of different strength promoters. Compared with the previous EP-bifido strains, the zwf-modified strains showed obvious differences in NADPH, NADH, and ATP synthesis levels. Among them, strain BP10BF accumulated 11.2 g/L of MVA after 72 h of fermentation and the molar conversion rate from glucose reached 62.2%. Second, pfkA was finely down-regulated by the clustered regularly interspaced short palindromic repeats interference (CRISPRi) system. The MVA yield of the regulated strain BiB1F was 8.53 g/L, and the conversion rate from glucose reached 68.7%. Conclusion This is the highest MVA conversion rate reported in shaken flask fermentation. The CRISPRi and promoter fine-tuning provided an effective strategy for metabolic flux redistribution in many metabolic pathways and promotes the chemicals production.

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