EC Number | Activating Compound | Comment | Organism | Structure |
---|---|---|---|---|
1.97.1.12 | additional information | isolation of thylakoids while in the continuous presence of reduced thiol reductant dithiothreitol (DTT), but not oxidized DTT, maintains high cyclic electron flow of photosystem I activity through an antimycin A-sensitive ferredoxin:quinone reductase (FQR). FQR mediated cyclic electron flow is highly sensitive to thylakoid isolation conditions, overview | Spinacia oleracea | |
1.97.1.12 | reduced DTT | does not reduce the plastoquinone pool directly, but is dependent on ferredoxin, consistent with the involvement of a ferredoxin-dependent reaction, most likely the ferredoxin:quinone reductase (FQR) | Spinacia oleracea |
EC Number | Localization | Comment | Organism | GeneOntology No. | Textmining |
---|---|---|---|---|---|
1.97.1.12 | chloroplast | - |
Spinacia oleracea | 9507 | - |
1.97.1.12 | thylakoid | - |
Spinacia oleracea | 9579 | - |
EC Number | Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
---|---|---|---|---|---|---|---|
1.97.1.12 | reduced plastocyanin + oxidized ferredoxin + hv | Spinacia oleracea | - |
oxidized plastocyanin + reduced ferredoxin | - |
? |
EC Number | Organism | UniProt | Comment | Textmining |
---|---|---|---|---|
1.97.1.12 | Spinacia oleracea | P80470 AND P06512 AND P10098 | psaA, psaB, and psaC | - |
EC Number | Source Tissue | Comment | Organism | Textmining |
---|---|---|---|---|
1.97.1.12 | leaf | - |
Spinacia oleracea | - |
EC Number | Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|---|
1.97.1.12 | additional information | thylakoids freshly isolated from spinach are assayed for their ability to generate a light driven proton gradient. While high rates of cyclic electron flow are observed in vivo, isolated thylakoids show only very slow rates, suggesting that the activity of a key complex is lost or downregulated upon isolation. Isolation of thylakoids in the complete absence of DTTRED leads to loss of CEF activity that is only partially restored by subsequent addition of 2 mM DTTRED, redox titration of CEF activity, overview | Spinacia oleracea | ? | - |
? | |
1.97.1.12 | reduced plastocyanin + oxidized ferredoxin + hv | - |
Spinacia oleracea | oxidized plastocyanin + reduced ferredoxin | - |
? |
EC Number | Synonyms | Comment | Organism |
---|---|---|---|
1.97.1.12 | PS I | - |
Spinacia oleracea |
1.97.1.12 | PSI | - |
Spinacia oleracea |
EC Number | pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
---|---|---|---|---|
1.97.1.12 | 7.6 | - |
assay at | Spinacia oleracea |
EC Number | Cofactor | Comment | Organism | Structure |
---|---|---|---|---|
1.97.1.12 | Ferredoxin | - |
Spinacia oleracea |
EC Number | General Information | Comment | Organism |
---|---|---|---|
1.97.1.12 | physiological function | the chloroplast must regulate supply of reducing equivalents and ATP to meet rapid changes in downstream metabolic demands. Cyclic electron flow around photosystem I (CEF) is proposed to balance the ATP/NADPH budget by using reducing equivalents to drive plastoquinone reduction, leading to the generation of proton motive force and subsequent ATP synthesis. Photosynthetic energy is stored by linear electron flow (LEF), which involves electron transfer through both photosystem II (PS II) and photosystem I (PS I). Multiple alternative electron pathways are identified or proposed including the water-water cycle, themalate shunt, the plastid terminal oxidase, and cyclic electron flow around photosystem I (CEF). Cyclic electron flow can alleviate an ATP deficit by passing electrons fromthe acceptor side of PS I back to PQ, driving the translocation of protons into the lumen without net reduction of NADP+. High rates of CEF are readily measured in vivo | Spinacia oleracea |