scholarly journals Characterization of the terminal stages of chlorophyll (ide) synthesis in etioplast membrane preparations

1975 ◽  
Vol 152 (3) ◽  
pp. 623-655 ◽  
Author(s):  
W T Griffiths
Keyword(s):  
Pentose Phosphate Pathway ◽  
Chlorophyll Biosynthesis ◽  
Pentose Phosphate ◽  
Activation Process ◽  
Active Complex ◽  
Sh Reagents ◽  
Intermittent Illumination ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Etioplast Membranes

1. Chlorophyll (ide) formation from protochlorophyll (ide) that is normally inactive was demonstrated in etioplast membranes isolated from maize and barlley plants, the process being dependent on intermittent illumination and the addition of NADPH. 2. The addition of NADPH to the membranes was shown to result in the conversion of inactive protochlorophyll (ide) absorbing at about 630 nm into a form(s) with light-absorption maxima at about 640 and 652 nm, both of which disappear when chlorophyll (ide) is formed on illumination. 3. The temperature-dependence of the activation process and its response to a variety of reagents were examined. From these, the conclusion is drawn that -SH groups are involved in the activation but in the active complex these are unavailable for reaction with -SH reagents. 4. Evidence is presented for the occurrence of glucose 6-phosphate dehydrogenase activity within etioplasts and the suggestion is made that the oxidative pentose phosphate pathway can provide the NADPH required for chlorophyll biosynthesis during the early stages of greening.

scholarly journals Glucose-6-phosphate dehydrogenase–6-phosphogluconolactonase: a unique bifunctional enzyme from Plasmodium falciparum

2011 ◽  
Vol 436 (3) ◽  
pp. 641-650 ◽  
Author(s):  
Esther Jortzik ◽  
Boniface M. Mailu ◽  
Janina Preuss ◽  
Marina Fischer ◽  
Lars Bode ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Pentose Phosphate Pathway ◽  
Drug Target ◽  
Pentose Phosphate ◽  
Bifunctional Enzyme ◽  
Functional Differences ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
First Time ◽  
Human Rbcs

The survival of malaria parasites in human RBCs (red blood cells) depends on the pentose phosphate pathway, both in Plasmodium falciparum and its human host. G6PD (glucose-6-phosphate dehydrogenase) deficiency, the most common human enzyme deficiency, leads to a lack of NADPH in erythrocytes, and protects from malaria. In P. falciparum, G6PD is combined with the second enzyme of the pentose phosphate pathway to create a unique bifunctional enzyme named GluPho (glucose-6-phosphate dehydrogenase–6-phosphogluconolactonase). In the present paper, we report for the first time the cloning, heterologous overexpression, purification and kinetic characterization of both enzymatic activities of full-length PfGluPho (P. falciparum GluPho), and demonstrate striking structural and functional differences with the human enzymes. Detailed kinetic analyses indicate that PfGluPho functions on the basis of a rapid equilibrium random Bi Bi mechanism, where the binding of the second substrate depends on the first substrate. We furthermore show that PfGluPho is inhibited by S-glutathionylation. The availability of recombinant PfGluPho and the major differences to hG6PD (human G6PD) facilitate studies on PfGluPho as an excellent drug target candidate in the search for new antimalarial drugs.

scholarly journals Molecular Characterization of the First Two Enzymes of the Pentose-phosphate Pathway of Trypanosoma brucei

2000 ◽  
Vol 275 (36) ◽  
pp. 27559-27565 ◽  
Author(s):  
Francis Duffieux ◽  
Joris Van Roy ◽  
Paul A.M. Michels ◽  
Fred R. Opperdoes
Keyword(s):  
Molecular Characterization ◽  
Trypanosoma Brucei ◽  
Pentose Phosphate Pathway ◽  
Pentose Phosphate

Identification and Characterization of Novel Human Glucose-6-Phosphate Dehydrogenase Inhibitors

2012 ◽  
Vol 18 (3) ◽  
pp. 286-297 ◽  
Author(s):  
Janina Preuss ◽  
Adam D. Richardson ◽  
Anthony Pinkerton ◽  
Michael Hedrick ◽  
Eduard Sergienko ◽  
...  
Keyword(s):  
High Throughput Screening ◽  
Basic Research ◽  
Pentose Phosphate ◽  
Screening Assay ◽  
High Throughput Screening Assay ◽  
Key Enzyme ◽  
Small Molecule Compound ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Identification And Characterization

Glucose-6-phosphate dehydrogenase (G6PD) is the key enzyme of the pentose phosphate pathway, converting glucose-6-phosphate to 6-phosphoglucono-δ-lactone with parallel reduction of NADP+. Several human diseases, including cancer, are associated with increased G6PD activity. To date, only a few G6PD inhibitors have been available. However, adverse side effects and high IC50 values hamper their use as therapeutics and basic research probes. In this study, we developed a high-throughput screening assay to identify novel human G6PD (hG6PD) inhibitors. Screening the LOPAC (Sigma-Aldrich; 1280 compounds), Spectrum (Microsource Discovery System; 1969 compounds), and DIVERSet (ChemBridge; 49 971 compounds) small-molecule compound collections revealed 139 compounds that presented ≥50% hG6PD inhibition. Hit compounds were further included in a secondary and orthogonal assay in order to identify false-positives and to determine IC50 values. The most potent hG6PD inhibitors presented IC50 values of <4 µM. Compared with the known hG6PD inhibitors dehydroepiandrosterone and 6-aminonicotinamide, the inhibitors identified in this study were 100- to 1000-fold more potent and showed different mechanisms of enzyme inhibition. One of the newly identified hG6PD inhibitors reduced viability of the mammary carcinoma cell line MCF10-AT1 (IC50 ~25 µM) more strongly than that of normal MCF10-A cells (IC50 >50 µM).

Respiratory enzyme activities during germination inBrassicaseed lots of differing vigour

1996 ◽  
Vol 6 (4) ◽  
pp. 165-174 ◽  
Author(s):  
Mary Bettey ◽  
W.E. Finch-Savage
Keyword(s):  
Oxygen Consumption ◽  
Pentose Phosphate Pathway ◽  
Sharp Increase ◽  
Artificial Aging ◽  
Pentose Phosphate ◽  
Untreated Seed ◽  
Seed Vigour ◽  
Regulatory Enzymes ◽  
Rate Of Oxygen Consumption ◽  
Glucose 6 Phosphate Dehydrogenase

AbstractThe rate of oxygen consumption by cabbage seeds increased on imbibition and there was a further sharp increase on germination. This was delayed in artificially aged seeds of low vigour. The increases in oxygen consumption reflect the increased oxidation of carbohydrates via respiratory pathways. The activities of key regulatory enzymes of glycolysis and the oxidative pentose phosphate pathway were measured in aged and unaged seed lots of cabbage. Differences in the activities of glucose 6-phosphate dehydrogenase and pyrophosphate:fructose 6-phosphate 1-phosphotransferase were correlated with the rate of germination (T50) in seed lots with large differences in seed vigour induced experimentally by artificial aging. However, the activities of these enzymes could not be used to distinguish between untreated seed lots which had smaller vigour differences apparent only under stress. The enzymes are presumably not controlling and determining seed vigour, but merely reflecting actual seed performance under the current conditions.

scholarly journals Regulation of the pentose phosphate cycle Cofactor that controls the inhibition of glucose-6-phosphate dehydrogenase by NADPH in rat liver

1986 ◽  
Vol 239 (3) ◽  
pp. 553-558 ◽  
Author(s):  
M Nogueira ◽  
G Garcia ◽  
C Mejuto ◽  
M Freire
Keyword(s):  
Ion Exchange ◽  
Rat Liver ◽  
Pentose Phosphate Pathway ◽  
Reductase Activity ◽  
Gel Filtration ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Pentose Phosphate ◽  
Glutathione Reductase Activity ◽  
Glucose 6 Phosphate Dehydrogenase

A cofactor of Mr 10(4), characterized as a polypeptide, was found to co-operate with GSSG to prevent the inhibition of glucose-6-phosphate dehydrogenase by NADPH, in order to ensure the operation of the oxidative phase of the pentose phosphate pathway, in rat liver [Eggleston & Krebs (1974) Biochem. J. 138, 425-435; Rodriguez-Segade, Carrion & Freire (1979) Biochem. Biophys. Res. Commun. 89, 148-154]. This cofactor has now been partially purified by ion-exchange chromatography and molecular gel filtration, and characterized as a protein of Mr 10(5). The lighter cofactor reported previously was apparently the result of proteolytic activity generated during the tissue homogenization. The heavier cofactor was unstable, and its amount increased in livers of rats fed on carbohydrate-rich diet. Since the purified cofactor contained no glutathione reductase activity, the involvement of this enzyme in the deinhibitory mechanism of glucose-6-phosphate dehydrogenase by NADPH should be ruled out.

Hexose-6-phosphate dehydrogenase in the endoplasmic reticulum

2010 ◽  
Vol 391 (1) ◽  
Author(s):  
Silvia Senesi ◽  
Miklos Csala ◽  
Paola Marcolongo ◽  
Rosella Fulceri ◽  
Jozsef Mandl ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Metabolic Syndrome ◽  
Endoplasmic Reticulum ◽  
Pentose Phosphate Pathway ◽  
Hydroxysteroid Dehydrogenase ◽  
Pyridine Nucleotide ◽  
Pentose Phosphate ◽  
The Metabolic Syndrome ◽  
Glucose 6 Phosphate Dehydrogenase

Abstract Hexose-6-phosphate dehydrogenase (H6PD) is a luminal enzyme of the endoplasmic reticulum that is distinguished from cytosolic glucose-6-phosphate dehydrogenase by several features. H6PD converts glucose-6-phosphate and NADP+ to 6-phosphogluconate and NADPH, thereby catalyzing the first two reactions of the pentose-phosphate pathway. Because the endoplasmic reticulum has a separate pyridine nucleotide pool, H6PD provides NADPH for luminal reductases. One of these enzymes, 11β-hydroxysteroid dehydrogenase type 1 responsible for prereceptorial activation of glucocorticoids, has been the focus of much attention as a probable factor in the pathomechanism of several human diseases including insulin resistance and the metabolic syndrome. This review summarizes recent advances related to the functions of H6PD.

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