scholarly journals Glycogen Metabolism Supports Photosynthesis Start through the Oxidative Pentose Phosphate Pathway in Cyanobacteria

2019 ◽  
Vol 182 (1) ◽  
pp. 507-517 ◽  
Author(s):  
Shrameeta Shinde ◽  
Xiaohui Zhang ◽  
Sonali P. Singapuri ◽  
Isha Kalra ◽  
Xianhua Liu ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Glycogen Metabolism ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway

scholarly journals Glycogen metabolism jump-starts photosynthesis through the oxidative pentose phosphate pathway (OPPP) in cyanobacteria

2019 ◽  
Author(s):  
Shrameeta Shinde ◽  
Sonali P. Singapuri ◽  
Xiaohui Zhang ◽  
Isha Kalra ◽  
Xianhua Liu ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Carbon Fixation ◽  
Transition Period ◽  
Dark Respiration ◽  
Electron Flow ◽  
Glycogen Metabolism ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Cellular Respiration ◽  
Dark Light

AbstractCyanobacteria experience drastic changes in their carbon metabolism under daily light-dark cycles. In the light, the Calvin-Benson cycle fixes CO2and divert excess carbon into glycogen storage. At night, glycogen is degraded to support cellular respiration. Dark-light transition represents a universal environmental stress for cyanobacteria and other photosynthetic lifeforms. Recent studies in the field revealed the essential genetic background necessary for the fitness of cyanobacteria during diurnal growth. However, the metabolic engagement behind the dark-light transition is not well understood. In this study, we discovered that glycogen metabolism can jump-start photosynthesis in the cyanobacteriumSynechococcus elongatusPCC 7942 when photosynthesis reactions start upon light. Compared to the wild type, the glycogen mutant (ΔglgC) showed much lower photosystem II efficiency and slower photosystem I-mediated cyclic electron flow rate when photosynthesis starts. Proteomics analyses indicated that glycogen is degraded through the oxidative pentose phosphate pathway (OPPP) during dark-light transition. We confirmed that the OPPP is essential for the initiation of photosynthesis, and further showed that glycogen degradation through the OPPP is likely to contribute to the activation of key Calvin-Benson cycle enzymes by modulating NADPH levels during the transition period. This ingenious strategy helps jump-start photosynthesis in cyanobacteria following dark respiration, and stabilize the Calvin-Benson cycle under fluctuating environmental conditions. It has evolutionary advantages for the survival of photosynthetic organisms using the Calvin-Benson cycle for carbon fixation.

scholarly journals Targeting oxidative pentose phosphate pathway prevents recurrence in mutant Kras colorectal carcinomas

PLoS Biology ◽  
2019 ◽  
Vol 17 (8) ◽  
pp. e3000425 ◽  
Author(s):  
WenChao Gao ◽  
YuTing Xu ◽  
Tao Chen ◽  
ZunGuo Du ◽  
XiuJuan Liu ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Colorectal Carcinomas

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 Beneficial effects of acute inhibition of the oxidative pentose phosphate pathway in the failing heart

2014 ◽  
Vol 306 (5) ◽  
pp. H709-H717 ◽  
Author(s):  
Claudio Vimercati ◽  
Khaled Qanud ◽  
Gianfranco Mitacchione ◽  
Danuta Sosnowska ◽  
Zoltan Ungvari ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Pentose Phosphate Pathway ◽  
Tissue Concentration ◽  
Glucose Consumption ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
Stroke Work ◽  
Failing Heart

In vitro studies suggested that glucose metabolism through the oxidative pentose phosphate pathway (oxPPP) can paradoxically feed superoxide-generating enzymes in failing hearts. We therefore tested the hypothesis that acute inhibition of the oxPPP reduces oxidative stress and enhances function and metabolism of the failing heart, in vivo. In 10 chronically instrumented dogs, congestive heart failure (HF) was induced by high-frequency cardiac pacing. Myocardial glucose consumption was enhanced by raising arterial glycemia to levels mimicking postprandial peaks, before and after intravenous administration of the oxPPP inhibitor 6-aminonicotinamide (80 mg/kg). Myocardial energy substrate metabolism was measured with radiolabeled glucose and oleic acid, and cardiac 8-isoprostane output was used as an index of oxidative stress. A group of five chronically instrumented, normal dogs served as control. In HF, raising glycemic levels from ∼80 to ∼170 mg/dL increased cardiac isoprostane output by approximately twofold, whereas oxPPP inhibition normalized oxidative stress and enhanced cardiac oxygen consumption, glucose oxidation, and stroke work. In normal hearts glucose infusion did not induce significant changes in cardiac oxidative stress. Myocardial tissue concentration of 6P-gluconate, an intermediate metabolite of the oxPPP, was significantly reduced by ∼50% in treated versus nontreated failing hearts, supporting the inhibitory effect of 6-aminonicotinamide. Our study indicates an important contribution of the oxPPP activity to cardiac oxidative stress in HF, which is particularly pronounced during common physiological changes such as postprandial glycemic peaks.

scholarly journals Lesions in the nuo Operon, Encoding NADH Dehydrogenase Complex I, Prevent PurF-Independent Thiamine Synthesis and Reduce Flux through the Oxidative Pentose Phosphate Pathway inSalmonella enterica Serovar Typhimurium

2000 ◽  
Vol 182 (1) ◽  
pp. 228-232 ◽  
Author(s):  
Kathy Claas ◽  
Shara Weber ◽  
Diana M. Downs
Keyword(s):  
Pentose Phosphate Pathway ◽  
Nadh Dehydrogenase ◽  
Pyridine Nucleotide ◽  
Growth Conditions ◽  
Pentose Phosphate ◽  
Oxidative Pentose Phosphate Pathway ◽  
New Class ◽  
Nucleotide Pools ◽  
Serovar Typhimurium ◽  
Cell Data

ABSTRACT In Salmonella enterica serovar Typhimurium, PurF-independent thiamine synthesis (or alternative pyrimidine biosynthesis) allows strains, under some growth conditions, to synthesize thiamine in the absence of the first step in the purine biosynthetic pathway. Mutations have been isolated in a number of loci that prevent this synthesis and thus result in an Apb−phenotype. Here we identify a new class of mutations that prevent PurF-independent thiamine synthesis and show that they are defective in the nuo genes, which encode the major, energy-generating NADH dehydrogenase of the cell. Data presented here indicated that anuo mutant has reduced flux through the oxidative pentose phosphate pathway that may contribute to, but is not sufficient to cause, the observed thiamine requirement. We suggest that reduction of the oxidative pentose phosphate pathway capacity in a nuomutant is an attempt to restore the ratio between reduced and oxidized pyridine nucleotide pools.

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