scholarly journals Overcompensation in Response to Herbivory in Arabidopsis thaliana: The Role of Glucose-6-Phosphate Dehydrogenase and the Oxidative Pentose-Phosphate Pathway

Genetics ◽  
2013 ◽  
Vol 195 (2) ◽  
pp. 589-598 ◽  
Author(s):  
Madhura H. Siddappaji ◽  
Daniel R. Scholes ◽  
Martin Bohn ◽  
Ken N. Paige
Keyword(s):  
Arabidopsis Thaliana ◽  
Pentose Phosphate Pathway ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Glucose 6 Phosphate Dehydrogenase

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.

II. Lokalisation von Enzymen des reduktiven und dem oxydativen Pentosephosphat-Zyklus in den Chloroplasten und Permeabilität der Chloroplasten-Membran gegenüber Metaboliten

1967 ◽  
Vol 22 (11) ◽  
pp. 1200-1215 ◽  
Author(s):  
U. Heber ◽  
U. W. Hallier ◽  
M. A. Hudson ◽  
B. von der Groeben ◽  
R. Ernst ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Enzyme Activities ◽  
Intracellular Localization ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Amino Acid Synthesis ◽  
Phosphogluconate Dehydrogenase ◽  
Chloroplast Membrane ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Isolated Chloroplasts

1. The interrelationship of metabolic activities in chloroplasts and cytoplasm of leaf cells of spinach, sugar beet and Elodea has been investigated. Different methods have been adopted to study the intracellular localization of enzymes and the flow of phosphorylated intermediates across the chloroplast membrane. The flow of substrates was investigated by determining the rates of the conversion of substrates added to aqueously isolated chloroplasts, prior to and after destruction of the outer chloroplast membrane. The observed differences yielded information as to whether a substrate could traverse the chloroplast membrane.Two methods mere used to investigate the localization of enzymes :a) The percentage distribution of photosynthetic and respiratory enzymes in chloroplasts and cytoplasm was calculated from data on enzyme activities in non-aqueous cell fractions.b) Low levels of enzymes in chloroplasts in the presence of high cytoplasmatic levels were detected by assaying enzyme activities in preparations of aqueously isolated chloroplasts prior to and after ultrasonic destruction of the outer chloroplast membrane.2. If chloroplasts are isolated in aqueous sucrose buffer, their outer membranes act as an efficient barrier against the penetration of NADP, RuDP, GAP and, in some but not all experiments, of FMP and GMP. PGA, DHAP and, probably to a lesser extent, aspartate, ɑ-ketoglutarate, oxaloacetate and FDP can traverse this membrane. Chloroplast membranes are significantly altered when isolated in NaCI-buffer systems and do not correspond to the in vivo situation.3. The conversion of Ri-5-P to RuDP occurs exclusively or nearly exclusively in the chloroplasts indicating that phosphoribulokinase and/or ribosephosphate isomerase are located only there.4. The conversion of Ri-5-P to GAP and SuMP, which is catalyzed by the enzymes ribosephosphate isomerase, xylulosephosphate epimerase and transketolase, proceeds likewise only or at least predominantly in the chloroplasts and not, or only to a small extent, in the cytoplasm.5. The major parts of glucose-6-phosphate dehydrogenase and of 6-phosphogluconate dehydrogenase reside in the cytoplasm. However, a small, but significant, level of these enzymes is to be found also in the chloroplasts. Hexokinase and transaldolase are also present there. Pyruvate kinase and phosphofructokinase appear to be absent from chloroplasts.6. Since, with the presence of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, hexokinase, transaldolase and enzymes of the Calvin cycle, the enzymic machinery of the oxidative pentose phosphate pathway is complete in the chloroplasts, the results suggest that chloroplasts are engaged in the oxidative decomposition of carbohydrates.7. In the dark the oxidative pentose phosphate pathway requires the control of NADPH formation and the transfer of hydrogen across the chloroplast membrane.8. The available data on the intracellular localization of enzymes and on the kinetics of the distribution of labelled intermediates show that the photosynthetic carbon cycle operates exclusively within the chloroplasts. There is nothing to suggest that enzymes of chloroplasts and cytoplasm cooperate in the cyclic regeneration of the carbon acceptor molecule. However, the existence of phosphorylated transport metabolites suggests that secondary reactions of photosynthesis such as sucrose and amino acid synthesis, which proceed, at least in part, outside the chloroplasts, are directly linked with chloroplastic reactions by activated (phosphorylated) intermediates.

The effect of soaking injury in bean seeds on aspects of the oxidative pentose phosphate pathway in embryonic axes

1992 ◽  
Vol 2 (1) ◽  
pp. 33-39 ◽  
Author(s):  
Johan C. Pretorius ◽  
J. G. Chris Small
Keyword(s):  
Pentose Phosphate Pathway ◽  
Causative Factor ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Embryonic Axes ◽  
Phosphogluconate Dehydrogenase ◽  
Saturated Water ◽  
Radicle Emergence ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Seed Coats

AbstractSubmerging Phaseolus vulgaris cv. Top Crop seeds in air-saturated water for 16 h markedly depresses subsequent germination. This is termed soaking injury. Soaking injury does not occur in seeds soaked in CO2-saturated water. Previous studies have shown that soaking injury can be alleviated by drying seeds or removing seed coats. Submergence therefore leads to a situation in bean seeds which is similar to secondary dormancy.As with dormant seeds, C6/C1 ratios of embryonic axes of seeds soaked in air-saturated water remained high (0.8–1.0) during and after soaking. This was paralleled by low activities of glucose-6-phosphate dehydrogenase (EC.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44). In axes of seeds soaked in CO2-saturated water and in unsoaked seeds C6/C1 ratios declined steadily during soaking/imbibition and reached values of around 0.3 after germination. Slight increases ofglucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities occurred in the pre-germination phase. This was followed by a massive increase after radicle emergence. Synthesis of the plastid isoenzymes was a post-germinative event.It appears that soaking injury depresses protein synthesis. Lack of oxidative pentose phosphate pathway activity appears to be a causative factor in soaking injury.

scholarly journals Activities of Catalase and Pentose Phosphate Pathway Dehydrogenases during Dormancy Release in Nectarine Seed

1990 ◽  
Vol 115 (6) ◽  
pp. 987-990 ◽  
Author(s):  
Hening Hu ◽  
Gary A. Couvillon
Keyword(s):  
Pentose Phosphate Pathway ◽  
Catalase Activity ◽  
Prunus Persica ◽  
Enzymic Activity ◽  
Pentose Phosphate ◽  
Significant Activity ◽  
Phosphogluconate Dehydrogenase ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Thiourea Treatment

The activities of catalase and of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), the two key enzymes in the pentose phosphate pathway (ppp), were measured in the seeds of Prunus persica (L.) Batsch var. nectarina Maxim `Nectarine 7'. The seeds were subjected to three imbibition treatments: 1) continuous 24C; 2) continuous 4C; and 3) application of thiourea (TU)/gibberellic acid (GA) at various concentrations to seed held at 24C then subsequently chilled at 4C. Treatments of continuous 24 or 4C indicated that catalase, G6PDH, and 6PGDH exhibited significant activity increases only when the seeds obtained germination potential, which occurred in the seeds chilled for 7 weeks at 4C. Seeds held at 24C did not germinate and showed little change with time in G6PDH and 6PGDH activity. There was only a slight increase in catalase activity beginning 3 weeks following treatment initiation and a decrease in activity following 13 weeks of treatment. Thiourea treatment resulted in an inhibition of catalase activity and a stimulation of G6PDH, but had no effect on 6PGDH activity. However, no correlation between enzymic activity and seed germination was found. The results strongly questioned the role of the ppp and catalase activity in dormancy control as previously hypothesized.

Regulation of D-glucose-6-phosphate dehydrogenase from Schizosaccharomyces pombe

1998 ◽  
Vol 76 (4) ◽  
pp. 645-648
Author(s):  
C Stan Tsai ◽  
Q Chen
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Pentose Phosphate Pathway ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Hill Coefficient ◽  
Negative Cooperativity ◽  
Hill Coefficients ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
The Hill

D-Glucose-6-phosphate dehydrogenase is a regulatory enzyme of the oxidative pentose phosphate pathway in Schizasaccharomyces pombe. The enzyme is subject to negative cooperative regulation by D-glucose-6-phosphate as characterized by the Hill coefficient of 0.68 ± 0.04. D-Glyceraldehyde-3-phosphate and D-ribulose-5-phosphate rectify the negative cooperativity as evidenced from a change in the Hill coefficients to 0.98 ± 0.05 and 1.02 ± 0.05, respectively. These pentose phosphate pathway intermediates also inhibit the enzyme competitively with respect to D-glucose-6-phosphate. Thus, D-glucose-6-phosphate dehydrogenase provides an avenue for regulating the partitioning of D-glucose between the redundant branches of the oxidative phosphate pathway in S. pombe.Key words: regulation, yeast, glucose-6-phosphate dehydrogenase.

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