scholarly journals Further observations on the Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase system

1993 ◽  
Vol 290 (2) ◽  
pp. 355-359 ◽  
Author(s):  
B J Whyte ◽  
P A Castelfranco
Keyword(s):  
Pentose Phosphate Pathway ◽  
Protoporphyrin Ix ◽  
Companion Paper ◽  
Pentose Phosphate ◽  
Chloroplast Pigments ◽  
Cyclization Process ◽  
Reconstituted System ◽  
Sugar Phosphates ◽  
Cytochrome P 450 ◽  
Monomethyl Ester

The Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase was strongly inhibited by CN- and N3- in a reconstituted system, but was inhibited slightly or not at all by the same reagents in intact developing chloroplasts. Known inhibitors of cytochrome P-450 processes showed no consistent effect. Benzoquinone and quinol, which can give rise to the same semiquinone by one-electron redox events, were strong inhibitors of the cyclase. It was previously shown that O2 and a source of electrons are required in the cyclization process. The substrates for the dehydrogenases of the pentose phosphate pathway (glucose 6-phosphate and 6-phosphogluconate) were effective reductants in the reconstituted system with supernatant that had been dialysed or passed through Sephadex G-50, in the absence of added NADP+. However, inhibitor studies suggested that the electrons from these sugar phosphates reached the cyclase system via NADPH. Therefore we infer the presence of protein-bound NADP+ that can be reduced by glucose 6-phosphate and 6-phosphogluconate and donate reducing equivalents to the cyclase system. This bound NADPH pool may be particularly effective in the cyclization process, owing to channeling. These findings are discussed in relation to the results of a companion paper [Whyte and Castelfranco (1993) Biochem. J. 290, 361-367] on the breakdown of chloroplast pigments in the same reconstituted system.

scholarly journals Profiling of Pentose Phosphate Pathway Intermediates in Blood Spots by Tandem Mass Spectrometry: Application to Transaldolase Deficiency

2003 ◽  
Vol 49 (8) ◽  
pp. 1375-1380 ◽  
Author(s):  
Jojanneke H J Huck ◽  
Eduard A Struys ◽  
Nanda M Verhoeven ◽  
Cornelis Jakobs ◽  
Marjo S van der Knaap
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Pentose Phosphate Pathway ◽  
Multiple Reaction Monitoring ◽  
Pentose Phosphate ◽  
Dihydroxyacetone Phosphate ◽  
Tandem Mass ◽  
Sugar Phosphate ◽  
Blood Spots ◽  
Sugar Phosphates

Abstract Background: Recently, several patients with abnormal polyol profiles in body fluids have been reported, but the origins of these polyols are unknown. We hypothesized that they are derived from sugar phosphate intermediates of the pentose phosphate pathway (PPP), and we developed a semiquantitative method for profiling of pentose phosphate pathway intermediates. Methods: Sugar phosphates in blood spots were simultaneously analyzed by liquid chromatography–tandem mass spectrometry using an ion-pair-loaded C18 HPLC column. The tandem mass spectrometer was operated in the multiple-reaction monitoring mode. Enzymatically prepared d-[13C6]glucose 6-phosphate was used as internal standard. The method was used to study sugar phosphates abnormalities in a patient affected with a deficiency of transaldolase (TALDO1; EC 2.2.1.2). Results: In control blood spots, dihydroxyacetone phosphate, pentulose 5-phosphates, pentose 5-phosphates, hexose 6-phosphates, and sedoheptulose 7-phosphate were detected. Detection limits ranged from ∼100 to ∼500 nmol/L. Glyceraldehyde 3-phosphate and erythrose 4-phosphate were undetectable. Intra- and interassay imprecision (CVs) were 10–17% and 12–21%, respectively. In blood from the TALDO1-deficient patient, sedoheptulose 7-phosphate was increased. Conclusions: The new method allows investigation of patients in whom a defect in the PPP is suspected. Measurements of sugar phosphate intermediates of the PPP may provide new insights into metabolic defects underlying the accumulating polyols.

[5-3H]glucose overestimates glycolytic flux in isolated working rat heart: role of the pentose phosphate pathway

2001 ◽  
Vol 280 (3) ◽  
pp. E502-E508 ◽  
Author(s):  
Gary W. Goodwin ◽  
David M. Cohen ◽  
Heinrich Taegtmeyer
Keyword(s):  
Steady State ◽  
Pentose Phosphate Pathway ◽  
Rat Heart ◽  
Physiological State ◽  
Pentose Phosphate ◽  
Glycolytic Flux ◽  
Precursor Pool ◽  
Rat Hearts ◽  
Extracellular Glucose ◽  
Sugar Phosphates

We set out to study the pentose phosphate pathway (PPP) in isolated rat hearts perfused with [5-3H]glucose and [1-14C]glucose or [6-14C]glucose (crossover study with 1- then 6- or 6- then 1-14C-labeled glucose). To model a physiological state, hearts were perfused under working conditions with Krebs-Henseleit buffer containing 5 mM glucose, 40 μU/ml insulin, 0.5 mM lactate, 0.05 mM pyruvate, and 0.4 mM oleate/3% albumin. The steady-state C1/C6 ratio (i.e., the ratio from [1-14C]glucose to [6-14C]glucose) of metabolites released by the heart, an index of oxidative PPP, was not different from 1 (1.06 ± 0.19 for14CO2, and 1.00 ± 0.01 for [14C]lactate + [14C]pyruvate, mean ± SE, n = 8). Hearts exhibited contractile, metabolic, and14C-isotopic steady state for glucose oxidation (14CO2production). Net glycolytic flux (net release of lactate + pyruvate) and efflux of [14C]lactate + [14C]pyruvate were the same and also exhibited steady state. In contrast, flux based on3H2O production from [5-3H]glucose increased progressively, reaching 260% of the other measures of glycolysis after 30 min. The3H/14C ratio of glycogen (relative to extracellular glucose) and sugar phosphates (representing the glycogen precursor pool of hexose phosphates) was not different from each other and was <1 (0.36 ± 0.01 and 0.43 ± 0.05 respectively, n = 8, P < 0.05 vs. 1). We conclude that both transaldolase and the L-type PPP permit hexose detritiation in the absence of net glycolytic flux by allowing interconversion of glycolytic hexose and triose phosphates. Thus apparent glycolytic flux obtained by3H2O production from [5-3H]glucose overestimates the true glycolytic flux in rat heart.

scholarly journals Conditional iron and pH-dependent activity of a non-enzymatic glycolysis and pentose phosphate pathway

2016 ◽  
Vol 2 (1) ◽  
pp. e1501235 ◽  
Author(s):  
Markus A. Keller ◽  
Andre Zylstra ◽  
Cecilia Castro ◽  
Alexandra V. Turchyn ◽  
Julian L. Griffin ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Metabolic Networks ◽  
Reaction Rates ◽  
Structural Features ◽  
Pentose Phosphate ◽  
Resonance Spectroscopy ◽  
Enzymatic Reactions ◽  
Evolutionary Origins ◽  
Sugar Phosphates ◽  
Neutral Conditions

Little is known about the evolutionary origins of metabolism. However, key biochemical reactions of glycolysis and the pentose phosphate pathway (PPP), ancient metabolic pathways central to the metabolic network, have non-enzymatic pendants that occur in a prebiotically plausible reaction milieu reconstituted to contain Archean sediment metal components. These non-enzymatic reactions could have given rise to the origin of glycolysis and the PPP during early evolution. Using nuclear magnetic resonance spectroscopy and high-content metabolomics that allowed us to measure several thousand reaction mixtures, we experimentally address the chemical logic of a metabolism-like network constituted from these non-enzymatic reactions. Fe(II), the dominant transition metal component of Archean oceanic sediments, has binding affinity toward metabolic sugar phosphates and drives metabolism-like reactivity acting as both catalyst and cosubstrate. Iron and pH dependencies determine a metabolism-like network topology and comediate reaction rates over several orders of magnitude so that the network adopts conditional activity. Alkaline pH triggered the activity of the non-enzymatic PPP pendant, whereas gentle acidic or neutral conditions favored non-enzymatic glycolytic reactions. Fe(II)-sensitive glycolytic and PPP-like reactions thus form a chemical network mimicking structural features of extant carbon metabolism, including topology, pH dependency, and conditional reactivity. Chemical networks that obtain structure and catalysis on the basis of transition metals found in Archean sediments are hence plausible direct precursors of cellular metabolic networks.

scholarly journals Ribose-5-Phosphate Biosynthesis in Methanocaldococcus jannaschii Occurs in the Absence of a Pentose-Phosphate Pathway

2005 ◽  
Vol 187 (21) ◽  
pp. 7382-7389 ◽  
Author(s):  
Laura L. Grochowski ◽  
Huimin Xu ◽  
Robert H. White
Keyword(s):  
Recent Work ◽  
Pentose Phosphate Pathway ◽  
Methanogenic Archaea ◽  
Protein Product ◽  
Pentose Phosphate ◽  
The Other ◽  
Methanocaldococcus Jannaschii ◽  
Cell Extracts ◽  
Ribulose Monophosphate Pathway ◽  
Sugar Phosphates

ABSTRACT Recent work has raised a question as to the involvement of erythrose-4-phosphate, a product of the pentose phosphate pathway, in the metabolism of the methanogenic archaea (R. H. White, Biochemistry 43:7618-7627, 2004). To address the possible absence of erythrose-4-phosphate in Methanocaldococcus jannaschii, we have assayed cell extracts of this methanogen for the presence of this and other intermediates in the pentose phosphate pathway and have determined and compared the labeling patterns of sugar phosphates derived metabolically from [6,6-2H2]- and [U-13C]-labeled glucose-6-phosphate incubated with cell extracts. The results of this work have established the absence of pentose phosphate pathway intermediates erythrose-4-phosphate, xylose-5-phosphate, and sedoheptulose-7-phosphate in these cells and the presence of d-arabino-3-hexulose-6-phosphate, an intermediate in the ribulose monophosphate pathway. The labeling of the d-ara-bino-3-hexulose-6-phosphate, as well as the other sugar-Ps, indicates that this hexose-6-phosphate was the precursor to ribulose-5-phosphate that in turn was converted into ribose-5-phosphate by ribose-5-phosphate isomerase. Additional work has demonstrated that ribulose-5-phosphate is derived by the loss of formaldehyde from d-arabino-3-hexulose-6-phosphate, catalyzed by the protein product of the MJ1447 gene.

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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