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MetaCyc Reactions Class: Electron-Transfer-Reactions

Summary:
Electron transfer reactions (ETRs) describe reactions that transfer electrons between substrates, which are thus involved in redox processes that oxidize and reduce some of the substrates. ETRs usually take place at membranes, because a key purpose of ETRs is to use the electron energy to build up a proton gradient across the membrane, which can then be used for energy generation by the cell, using ATP synthesis driven by the proton gradient. ETRs very often involve the pool of membrane-bound quinone substrates, which can shuttle electrons to or from an ETR.

All ETRs are composite reactions, because they involve at least two redox half reactions. These half reactions involve explicit electrons, which cannot occur freely. Thus, the half reactions have to be paired up, with the result that the electrons are used only internally to connect the half reactions, and are not visible as substrates of the ETR.

Sometimes, a proton transport reaction can also be a sub-reaction of the ETR, to represent so-called vectoral proton movement. In the vectoral case, protons are actively pumped across the membrane, using energy extracted from the redox processes. The proton transport reaction is not directly connected to the redox half reactions in the pathway representation of the composite reaction.

Because ETRs tend to occur at membranes, substrates that are not in the default compartment (the cytoplasm) need to have compartment information associated by means of value annotations. The exception to this are the membrane-bound quinone substrates, which are always assumed to reside in the membrane itself.

Parent Classes:
Composite Reactions

Instances:
1.1.5.2: D-glucopyranose[periplasm] + a ubiquinone[inner membrane] → D-glucono-1,5-lactone[periplasm] + an ubiquinol[inner membrane],
1.1.5.3: sn-glycerol 3-phosphate[in] + an electron-transfer quinone[membrane] → glycerone phosphate[in] + an electron-transfer quinol[membrane],
1.1.5.3: sn-glycerol 3-phosphate[in] + a ubiquinone[membrane] → glycerone phosphate[in] + an ubiquinol[membrane],
1.1.5.3: sn-glycerol 3-phosphate + a menaquinone[inner membrane] → glycerone phosphate + a menaquinol[inner membrane],
1.1.5.4: (S)-malate + an electron-transfer quinone[inner membrane] → oxaloacetate + an electron-transfer quinol[inner membrane],
1.1.5.6: formate[periplasm] + a menaquinone[inner membrane] + 2 H+ → CO2[periplasm] + a menaquinol[inner membrane] + H+[periplasm],
1.1.5.9: D-glucopyranose[out] + an electron-transfer quinone[membrane] + 2 H+[in] → D-glucono-1,5-lactone[out] + an electron-transfer quinol[membrane] + 2 H+[out],
1.1.5.-: (R)-lactate + a ubiquinone[inner membrane] → pyruvate + an ubiquinol[inner membrane],
1.2.5.1: pyruvate + a ubiquinone[inner membrane] + H2O → CO2 + acetate + an ubiquinol[inner membrane],
1.3.5.1: caldariellaquinone[membrane] + succinate[in] → caldariellaquinol[membrane] + fumarate[in],
1.3.5.1: succinate[in] + an electron-transfer quinone[membrane] → fumarate[in] + an electron-transfer quinol[membrane],
1.3.5.1: succinate[in] + a ubiquinone[membrane] → fumarate[in] + an ubiquinol[membrane],
1.3.5.2: (S)-dihydroorotate + an electron-transfer quinone[inner membrane] → orotate + an electron-transfer quinol[inner membrane],
1.3.5.2: (S)-dihydroorotate + a menaquinone[inner membrane] → orotate + a menaquinol[inner membrane],
1.3.5.2: (S)-dihydroorotate[in] + a ubiquinone[membrane] → orotate[in] + an ubiquinol[membrane],
1.3.5.3: protoporphyrin IX + 3 a menaquinol[inner membrane] ← protoporphyrinogen IX + 3 a menaquinone[inner membrane],
1.3.5.4: fumarate[in] + a menaquinol[membrane] ↔ succinate[in] + a menaquinone[membrane],
1.3.5.4: succinate[in] + an electron-transfer quinone[membrane] ← fumarate[in] + an electron-transfer quinol[membrane],
1.3.5.4: fumarate[mitochondrial lumen] + a rhodoquinol[CCO-MIT-IM-SPC-CCO-MIT-LUM] → succinate[mitochondrial lumen] + a rhodoquinone[CCO-MIT-IM-SPC-CCO-MIT-LUM],
1.4.5.1: a D-amino acid[in] + an electron-transfer quinone[membrane] + H2O[in] → a 2-oxo carboxylate[in] + ammonium[in] + an electron-transfer quinol[membrane],
1.4.5.-: D-alanine + an electron-transfer quinone[inner membrane] + H2O → ammonium + pyruvate + an electron-transfer quinol[inner membrane],
1.5.5.1: a reduced electron-transfer flavoprotein[mitochondrial lumen] + a ubiquinone[mitochondrial inner membrane] → an oxidized electron-transfer flavoprotein[mitochondrial lumen] + an ubiquinol[mitochondrial inner membrane] + H+[mitochondrial lumen],
1.5.5.2: L-proline + an electron-transfer quinone[inner membrane] → (S)-1-pyrroline-5-carboxylate + an electron-transfer quinol[inner membrane] + H+,
1.5.5.2: L-proline[in] + a ubiquinone[membrane] → (S)-1-pyrroline-5-carboxylate[in] + an ubiquinol[membrane] + H+[in],
1.5.5.2: L-proline + a ubiquinone[inner membrane] → (S)-1-pyrroline-5-carboxylate + an ubiquinol[inner membrane] + H+,
1.5.5.-: trans-4-hydroxy-L-proline[in] + an electron-transfer quinone[membrane] → (3R,5S)-1-pyrroline-3-hydroxy-5-carboxylate[in] + an electron-transfer quinol[membrane] + H+[in],
1.6.5.2: an electron-transfer quinone[inner membrane] + NAD(P)H + H+ → an electron-transfer quinol[inner membrane] + NAD(P)+,
1.6.5.3: NADH[in] + a ubiquinone[membrane] + 5 H+[in] ↔ NAD+[in] + an ubiquinol[membrane] + 4 H+[out],
1.6.5.9: NADH[in] + a ubiquinone[membrane] + H+[in] → NAD+[in] + an ubiquinol[membrane],
1.6.5.10: NADPH + an electron-transfer quinone[inner membrane] + H+ → NADP+ + an electron-transfer quinol[inner membrane],
1.6.5.-: NADH + a menaquinone[inner membrane] + 5 H+ → NAD+ + a menaquinol[inner membrane] + 4 H+[periplasm],
1.7.2.1: nitrite[periplasm] + a reduced cytochrome c551[periplasm] + 2 H+[periplasm] ↔ nitric oxide[periplasm] + an oxidized cytochrome c551[periplasm] + H2O[periplasm],
1.7.2.2: nitrite[out] + 6 a reduced c-type cytochrome[out] + 8 H+[out] → ammonium[out] + 6 an oxidized c-type cytochrome[out] + 2 H2O[out],
1.7.2.3: trimethylamine N-oxide[periplasm] + a menaquinol[inner membrane] + H+[periplasm] → trimethylamine[periplasm] + a menaquinone[inner membrane] + H2O[periplasm],
1.7.2.4: 2 a reduced c-type cytochrome[periplasm] + nitrous oxide[periplasm] + 2 H+[periplasm] → 2 an oxidized c-type cytochrome[periplasm] + N2[periplasm] + H2O[periplasm],
1.7.2.5: 2 nitric oxide[periplasm] + 2 a reduced c-type cytochrome[periplasm] + 2 H+[periplasm] ↔ nitrous oxide[periplasm] + 2 an oxidized c-type cytochrome[periplasm] + H2O[periplasm],
1.7.2.6: 4 an oxidized c-type cytochrome[out] + hydroxylamine[in] + H2O[in] → 4 a reduced c-type cytochrome[out] + nitrite[in] + 5 H+[in],
1.7.2.-: 2 an oxidized c-type cytochrome[out] + nitrite[in] + H2O[in] → 2 a reduced c-type cytochrome[out] + nitrate[in] + 2 H+[in],
1.7.5.1: nitrate + a menaquinol[inner membrane] + 2 H+ → nitrite + a menaquinone[inner membrane] + H2O + 2 H+[periplasm],
1.7.5.1: nitrate + an electron-transfer quinol[inner membrane] ↔ nitrite + an electron-transfer quinone[inner membrane] + H2O,
1.7.5.1: nitrate[periplasm] + an ubiquinol[inner membrane] → nitrite[periplasm] + a ubiquinone[inner membrane] + H2O[periplasm],
1.7.5.1: nitrate[periplasm] + a menaquinol[inner membrane] → nitrite[periplasm] + a menaquinone[inner membrane] + H2O[periplasm],
1.7.5.1: nitrate + an ubiquinol[inner membrane] + 2 H+ → nitrite + a ubiquinone[inner membrane] + 2 H+[periplasm] + H2O,
1.8.2.2: 2 an oxidized c-type cytochrome[periplasm] + 2 thiosulfate[periplasm] → tetrathionate[periplasm] + 2 a reduced c-type cytochrome[periplasm] + 2 H+[periplasm],
1.8.5.3: dimethyl sulfide[periplasm] + a menaquinone[inner membrane] + H2O[periplasm] ← dimethyl sulfoxide[periplasm] + a menaquinol[inner membrane],
1.9.3.1: 4 a reduced c-type cytochrome[out] + oxygen[in] + 8 H+[in] → 4 an oxidized c-type cytochrome[out] + 4 H+[out] + 2 H2O[in],
1.9.3.1: 4 a reduced c-type cytochrome[periplasm] + oxygen + 8 H+ → 4 an oxidized c-type cytochrome[periplasm] + 4 H+[periplasm] + 2 H2O,
1.9.6.1: nitrate[periplasm] + 2 a reduced c-type cytochrome[periplasm] + 2 H+[periplasm] → nitrite[periplasm] + 2 an oxidized c-type cytochrome[periplasm] + H2O[periplasm],
1.10.2.2: 2 an oxidized c-type cytochrome[out] + an electron-transfer quinol[membrane] → 2 a reduced c-type cytochrome[out] + an electron-transfer quinone[membrane] + 2 H+[in],
1.10.2.2: 2 an oxidized c-type cytochrome[out] + a menaquinol[membrane] → 2 a reduced c-type cytochrome[out] + a menaquinone[membrane] + 2 H+[in],
1.10.2.2: 2 an oxidized c-type cytochrome[out] + an ubiquinol[membrane] ↔ 2 a reduced c-type cytochrome[out] + a ubiquinone[membrane] + 2 H+[out],
1.10.2.2: 2 a reduced CycA1 cytochrome[periplasm] + a ubiquinone[inner membrane] + 4 H+ → 2 an oxidized CycA1 cytochrome[periplasm] + an ubiquinol[inner membrane] + 2 H+[periplasm],
1.10.3.9: 2 a plastoquinol[chloroplast thylakoid membrane] + 4 H+[chloroplast thylakoid lumen] + oxygen[chloroplast thylakoid lumen] ← hν + 2 a plastoquinone[chloroplast thylakoid membrane] + 4 H+[chloroplast stroma] + 2 H2O[chloroplast thylakoid lumen],
1.10.3.10: 2 an ubiquinol[inner membrane] + oxygen + 5 H+ → 2 a ubiquinone[inner membrane] + 2 H2O + 5 H+[periplasm],
1.10.3.11: 2 an ubiquinol[mitochondrial inner membrane] + oxygen[mitochondrial lumen] → 2 a ubiquinone[mitochondrial inner membrane] + 2 H2O[mitochondrial lumen],
1.10.3.12: 2 a menaquinol[membrane] + oxygen[in] + 8 H+[in] → 2 a menaquinone[membrane] + 8 H+[out] + 2 H2O[in],
1.10.3.13: 2 caldariellaquinol[membrane] + H+[in] + oxygen[in] → 2 caldariellaquinone[membrane] + H+[out] + 2 H2O[in],
1.10.3.14: 2 an ubiquinol[inner membrane] + 4 H+ + oxygen → 2 a ubiquinone[inner membrane] + 4 H+[periplasm] + 2 H2O,
1.10.9.1: 2 an oxidized plastocyanin[chloroplast thylakoid lumen] + a plastoquinol[chloroplast thylakoid membrane] + 2 H+[chloroplast stroma] → 2 a reduced plastocyanin[chloroplast thylakoid lumen] + a plastoquinone[chloroplast thylakoid membrane] + 4 H+[chloroplast thylakoid lumen],
1.12.99.6: a menaquinone[inner membrane] + 2 H+ + H2[periplasm] → a menaquinol[inner membrane] + 2 H+[periplasm],
1.14.99.39: ammonia[in] + an reduced unknown electron acceptor[in] + oxygen[in] → hydroxylamine[in] + an oxidized unknown electron acceptor[in] + H2O[in],
1.16.5.1: L-ascorbate[in] + Fe3+[out] → monodehydroascorbate radical[in] + Fe2+[out],
1.16.9.1: Fe3+[extracellular space] + a reduced rusticyanin[periplasm] ← Fe2+[extracellular space] + an oxidized rusticyanin[periplasm],
1.18.1.2: 2 a reduced ferredoxin [iron-sulfur] cluster[out] + NADP+[in] + H+[in] → 2 an oxidized ferredoxin [iron-sulfur] cluster[out] + NADPH[in],
1.20.2.1: 2 a reduced c-type cytochrome[periplasm] + arsenate + 3 H+ ← 2 an oxidized c-type cytochrome[periplasm] + arsenite + H2O,
1.20.9.1: 2 a reduced azurin[periplasm] + arsenate[extracellular space] + 3 H+[extracellular space] ← 2 an oxidized azurin[periplasm] + arsenite[extracellular space] + H2O[extracellular space],
1.97.1.12: an oxidized plastocyanin[chloroplast thylakoid lumen] + a reduced ferredoxin [iron-sulfur] cluster[chloroplast stroma] ← hν + a reduced plastocyanin[chloroplast thylakoid lumen] + an oxidized ferredoxin [iron-sulfur] cluster[chloroplast stroma],
1.97.1.-: tetrathionate[periplasm] + an reduced unknown electron acceptor + 2 H+[periplasm] ↔ 2 thiosulfate[periplasm] + an oxidized unknown electron acceptor + 2 H+,
NADH[in] + a menaquinone[membrane] + H+[in] → NAD+[in] + a menaquinol[membrane],
an oxidized Cyc1 cytochrome[periplasm] + a reduced rusticyanin[periplasm] → an oxidized rusticyanin[periplasm] + a reduced Cyc1 cytochrome[periplasm],
a reduced rusticyanin[periplasm] + an oxidized CycA1 cytochrome[periplasm] → a reduced CycA1 cytochrome[periplasm] + an oxidized rusticyanin[periplasm]


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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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