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Literature summary extracted from

  • Strand, D.; Fisher, N.; Davis, G.; Kramer, D.
    Redox regulation of the antimycin A sensitive pathway of cyclic electron flow around photosystem I in higher plant thylakoids (2016), Biochim. Biophys. Acta, 1857, 1-6 .
No PubMed abstract available

Activating Compound

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

Localization

EC Number Localization Comment Organism GeneOntology No. Textmining
1.97.1.12 chloroplast
-
 Spinacia oleracea 9507
-
1.97.1.12 thylakoid
-
 Spinacia oleracea 9579
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Natural Substrates/ Products (Substrates)

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
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
1.97.1.12 Spinacia oleracea P80470 AND P06512 AND P10098 psaA, psaB, and psaC
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Source Tissue

EC Number Source Tissue Comment Organism Textmining
1.97.1.12 leaf
-
 Spinacia oleracea
-

Substrates and Products (Substrate)

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 ?
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 ?
1.97.1.12 reduced plastocyanin + oxidized ferredoxin + hv
-
 Spinacia oleracea oxidized plastocyanin + reduced ferredoxin
-
 ?

Synonyms

EC Number Synonyms Comment Organism
1.97.1.12 PS I
-
 Spinacia oleracea
1.97.1.12 PSI
-
 Spinacia oleracea

pH Optimum

EC Number pH Optimum Minimum pH Optimum Maximum Comment Organism
1.97.1.12 7.6
-
 assay at Spinacia oleracea

Cofactor

EC Number Cofactor Comment Organism Structure
1.97.1.12 Ferredoxin
-
 Spinacia oleracea

General Information

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