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
Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society
127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Power and Electrical Engineering
18.01.2017 | Materials Sciences
18.01.2017 | Life Sciences