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Towards the mechanism of cell respiration
April 06, 2006Researchers at the Institute of Biotechnology of the University of Helsinki have for the first time identified an internal electron transfer reaction that initiates the proton pump mechanism of the respiratory enzyme. These new results are published in the Thursday (April 6th) issue of Nature.
The functions of the lungs, the blood circulation, and the red blood cells in respiration are only an overture to the physicochemical reaction in the cells where oxygen is reduced to water. Oxygen consumption in cell respiration is a strictly controlled enzymatic reaction in the inner mitochondrial membrane. The respiratory enzyme cytochrome oxidase functions as a proton pump that transduces free energy from oxygen reduction to an electrochemical proton gradient, which is utilised by another enzyme to produce ATP, the cells' general energy currency.
The results by the research group of academy professor MĂårten Wikström revealed the coupling between the function of the proton pump and oxygen reduction: an internal electron transfer initiates the first stage of the pump mechanism. "This finding opens the door towards understanding the mechanism, which has been the subject of research for almost 30 years", Wikström says.
The proton pump of cytochrome oxidase is closely linked to the process by which the energy of foodstuffs is transduced into a useful energy source for our cells. Another enzyme makes use of the proton gradient generated by the pump, synthesising adenosine triphosphate (ATP) that powers energy-requiring functions such as muscle contraction and nerve impulses. The central biological importance of this system is evident, for example from the almost immediate death that follows from blocking cell respiration, e.g. by cyanide.
Cytochrome oxidase functions as an energy transducer in much the same way as a fuel cell. It is a biological "nanomachine" that has evolved over billions of years, and has an efficiency better than 90%.
Wikström and his colleagues study both the chemical reaction and the proton pump of cytochrome oxidase by biophysical techniques with a time resolution less than one microsecond. In this way it has been possible to monitor the enzyme's functions in real time. It takes about one millisecond for the respiratory enzyme to reduce one oxygen molecule to water. This time includes all the partial reactions, and also the efficient energy-transducing mechanism.
University of Helsinki
The proton pump of cytochrome oxidase is closely linked to the process by which the energy of foodstuffs is transduced into a useful energy source for our cells. Another enzyme makes use of the proton gradient generated by the pump, synthesising adenosine triphosphate (ATP) that powers energy-requiring functions such as muscle contraction and nerve impulses. The central biological importance of this system is evident, for example from the almost immediate death that follows from blocking cell respiration, e.g. by cyanide.
Cytochrome oxidase functions as an energy transducer in much the same way as a fuel cell. It is a biological "nanomachine" that has evolved over billions of years, and has an efficiency better than 90%.
Wikström and his colleagues study both the chemical reaction and the proton pump of cytochrome oxidase by biophysical techniques with a time resolution less than one microsecond. In this way it has been possible to monitor the enzyme's functions in real time. It takes about one millisecond for the respiratory enzyme to reduce one oxygen molecule to water. This time includes all the partial reactions, and also the efficient energy-transducing mechanism.
University of Helsinki
Unstable proteins can cause premature ageing
The normal ageing process has long been linked to problems with cell respiration, the process through which the cells extract energy from nutrients.
Key protein in cellular respiration discovered
Many diseases derive from problems with cellular respiration, the process through which cells extract energy from nutrients. Researchers at Karolinska Institutet have now discovered a new function for a protein in the mitochondrion - popularly called the cell's power station - that plays a key part in cell respiration.
Body's "wonder gas" could tackle asthma and heart disease
The body's all-pervasive "wonder gas" nitric oxide is giving up its secrets to a high-powered team of researchers at the Wolfson Institute for Biomedical Research at University College London and the knowledge may lead to new treatments for asthma, heart disease, joint problems and a range of other conditions. The work is being led by Professor Salvador Moncada, who first discovered nitric oxide in biological systems in 1987. Until then it was thought the gas was just a waste product of the body - but now scientists know it is manufactured to promote a host of functions, and its importance grows with each new discovery. Nitric oxide has several very significant roles - and new ones
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