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An electron transport chain (ETC [1]) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H + ions) across a membrane.
Reaction catalyzed by an oxidase, note the reduction of oxygen as the electron acceptor. Dehydrogenase and oxidase are easily distinguishable if one considers the electron acceptor. An oxidase will remove electrons from a substrate as well, but only uses oxygen as its electron acceptor. One such reaction is: AH 2 + O 2 ↔ A + H 2 O 2.
There are three energy-transducing enzymes in the electron transport chain - NADH:ubiquinone oxidoreductase (complex I), Coenzyme Q – cytochrome c reductase (complex III), and cytochrome c oxidase (complex IV). [1] Complex I is the largest and most complicated enzyme of the electron transport chain. [2] The reaction catalyzed by complex I is:
NADH dehydrogenase is used in the electron transport chain for generation of ATP. The EC term NADH dehydrogenase (quinone) (EC 1.6.5.11) is defined for NADH dehydrogenases that use a quinone (excluding ubiquinone) as the acceptor. The EC term NADH dehydrogenase (ubiquinone) (EC 7.1.1.2) is defined for those with ubiquinone as the acceptor.
Mitochondrial glycerol-3-phosphate dehydrogenase (GPD2), catalyzes the irreversible oxidation of glycerol-3-phosphate to dihydroxyacetone phosphate and concomitantly transfers two electrons from FAD to the electron transport chain. GPD2 consists of 4 identical subunits.
NADH-coenzyme Q oxidoreductase, also known as NADH dehydrogenase or complex I, is the first protein in the electron transport chain. [18] Complex I is a giant enzyme with the mammalian complex I having 46 subunits and a molecular mass of about 1,000 kilodaltons (kDa). [ 19 ]
Enzymatic reaction catalyzed by NDH-2. In yellow is represented the protein surface, sitting in the membrane (in gray) NDH-2, also known as type II NADH:quinone oxidoreductase or alternative NADH dehydrogenase, is an enzyme (EC: 1.6.99.3) which catalyzes the electron transfer from NADH (electron donor) to a quinone (electron acceptor), being part of the electron transport chain. [1]
The glycerol phosphate shuttle was first characterized as a major route of mitochondrial hydride transport in the flight muscles of blow flies. [5] [6] It was initially believed that the system would be inactive in mammals due to the predominance of lactate dehydrogenase activity over glycerol-3-phosphate dehydrogenase 1 (GPD1) [5] [7] until high GPD1 and GPD2 activity were demonstrated in ...