Oxygen-consuming organisms obtain energy through cellular respiration, which is the transformation of carbohydrates and oxygen into carbon dioxide and water. This process also produces toxic oxygen radicals which must be decomposed immediately, as they would otherwise cause damage to cells.
Scientists from the Max Planck Institute for Molecular Genetics in Berlin have now discovered a mechanism, with whose help cells can coordinate respiratory activity and the degradation of free radicals. Thus, the cells prepare their metabolism for free radicals before they even arise.
Cellular respiration is a very efficient process through which a lot of energy is generated from a few sugar molecules and oxygen. However, up to two percent of the oxygen used in this process is transformed into superoxide, a free radical that is toxic to cells. A considerable proportion of this superoxide evades the respiratory chain of the mitochondria and poses a threat to biological macromolecules like DNA, RNA, proteins and fatty acids.
However, evolution has equipped eukaryotic cells with comprehensive mechanisms that can decompose free radicals which arise in the cell and therefore prevent damage to the cell. These mechanisms work extremely efficiently and are well coordinated so that, contrary to popular belief, the treatment of healthy tissue with natural or synthetic antioxidants can disrupt the natural balance and, at worst, damage cells and accelerate the aging process.
Researchers at the Max Planck Institute for Molecular Genetics compared respiring and non-respiring yeast cells. When respiration was activated, there was a direct increase in the cells’ tolerance to oxidised substances; however, contrary to expectation, this was not accompanied by a rise in the concentration of free radicals. This proved that respiring cells are entirely capable of dealing with the increased formation of free radicals and keeping them at the level of the non-respiring cells.
According to the researchers, a hitherto undiscovered feedback mechanism located within a central metabolic pathway is responsible for this process. The carbohydrate-degrading enzyme pyruvate kinase regulates the respiratory activity of yeast cells. It is less active in respiring cells and this leads to the accumulation of its substrate phosphoenolpyruvate. The accumulation of this substance inhibits another glycolytic enzyme, triosephosphate isomerase. The researchers were already very familiar with this enzyme: they had previously discovered that a low level of activity of this enzyme provides protection against free radicals. “If we block this feedback mechanism artificially while activating respiration, the free radical concentration increased significantly and damaged proteins and mitochondria. This tells us that cells can predict when the radical production will rise and adapt their metabolism before the free radicals are even produced,” explains Markus Ralser, researcher at the Max Planck Institute for Molecular Genetics and the University of Cambridge.
This discovery may prove to be of particular significance for cancer research. The enzyme pyruvate kinase is partly responsible for the fact that tumour cells usually respire less and thus have a higher rate of sugar metabolism than healthy tissue. This effect is named after Otto Warburg, who was the first scientist to demonstrate this higher rate of sugar metabolism in cancer cells in the 1920s. The Max Planck researchers hope that it will be possible to use this newly discovered feedback mechanism to cause targeted nutrition deficiency in tumour cells and render them more vulnerable in this way.
ContactDr. Patricia Marquardt
Cell Metabolism, September 7, 2011
Dr. Patricia Marquardt | Max-Planck-Institute
What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society
Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
23.08.2017 | Life Sciences
23.08.2017 | Life Sciences
23.08.2017 | Physics and Astronomy