[Respiratory oxidases: the enzymes which use most of the oxygen which living things breathe].
The respiratory oxidases are the last enzymes of the aerobic respiratory chain. They catalize the reduction of molecular oxygen to water, with generation of an electrochemical gradient useful for the energy demanding cellular processes. Most of the oxidases belong to the heme-copper superfamily. They possess a heme-copper center, constituted of a high spin heme and a CuB center, where the reduction of oxygen takes place and probably where the link to proton pumping is located. The superfamily is divided in two classes: the quinol- and the cytochrome c-oxidases. The latter are divided in the aa3 and the cbb3-type cytochrome c oxidases. The main difference between quinol- and the aa3-type cytochrome c-oxidases is the CuA center, which is absent in the quinol oxidases. The cbb3-type cytochrome oxidases have the binuclear center, but lack the CuA center. They also does not have the classical subunits II and III. These differences seem not to affect the oxygen reduction or the proton pumping. Probably the oxidases have evolved from some denitrification enzymes and prior the photosynthetic process. Also is possible that the cbb3-type cytochrome oxidases or others very similar have been the first oxidases to appear.
Department of Medical Chemistry, University of Helsinki, Finland. mtoledo@ifcsun1.ifisiol.unam.mx
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Toledo-Cuevas
D000332:Aerobiosis; D003574:Cytochrome c Group / Q000145:classification / Q000235:genetics / Q000502:physiology; D004272:DNA, Mitochondrial / Q000235:genetics; D004579:Electron Transport; D005057:Eukaryotic Cells / Q000201:enzymology; D019143:Evolution, Molecular; D006418:Heme / Q000737:chemistry / Q000502:physiology; D007527:Isoenzymes / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000502:physiology; D010085:Oxidative Phosphorylation; D010088:Oxidoreductases / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D011387:Prokaryotic Cells / Q000201:enzymology; D012119:Respiration; D013329:Structure-Activity Relationship
D003574:Cytochrome c Group; D004272:DNA, Mitochondrial; D007527:Isoenzymes; D006418:Heme; D010088:Oxidoreductases; D010100:Oxygen