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discounted EARLY registration ends Dec 31, 2014
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discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
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MetaCyc Compound Class: a plastoquinol

Superclasses: a redox electron carrier Membrane-Electron-Carriers an electron-transfer-related quinol
an aromatic compound a quinol an electron-transfer-related quinol

Summary:
Plastoquinones are found in the chloroplasts of higher plants, red, brown and green algae, and in cyanobacteria, and are important members of the photosynthetic electron transfer chain, where they carry electrons from photosystem II to the cytochrome b6f complex. Plastoquinones also serve as cofactors involved in the desaturation of phytoene in the synthesis of carotenoids (see trans-lycopene biosynthesis II (plants)).

They are analogs of ubiquinones (Coenzyme Q), with two methyl groups substituting the methoxy groups found in Q. Plastoquinone can function as acceptor/donor for one or two electrons. The fully reduced form is called a plastoquinol.

Plastoquinone was isolated originally in 1946 from alfalfa, but was not identified at the time. It was rediscovered in 1959 and its structure was described in the same year (see [Collins81]).

Please note that the structure shown here is that of plastoquinol-9 and is not accurate for this generic class of compounds, which contains plastoquinols with different side-chain lengths.

Chemical Formula: C53H82O2

Instances:
plastoquinol-9

Molecular Weight: 751.23 Daltons

Monoisotopic Molecular Weight: 750.6314818764 Daltons

SMILES: CC(C)=CCCC(=CCCC(C)=CCCC(=CCCC(=CCCC(=CCCC(=CCCC(C)=CCCC(C)=CCC1(C=C(C(=C(C=1O)C)C)O))C)C)C)C)C

InChI: InChI=1S/C53H82O2/c1-40(2)21-13-22-41(3)23-14-24-42(4)25-15-26-43(5)27-16-28-44(6)29-17-30-45(7)31-18-32-46(8)33-19-34-47(9)35-20-36-48(10)37-38-51-39-52(54)49(11)50(12)53(51)55/h21,23,25,27,29,31,33,35,37,39,54-55H,13-20,22,24,26,28,30,32,34,36,38H2,1-12H3/b41-23+,42-25+,43-27+,44-29+,45-31+,46-33+,47-35+,48-37+

Standard Gibbs Free Energy of Change Formation (ΔfG in kcal/mol): 1039.152 Inferred by computational analysis [Latendresse13]

Reactions known to consume the compound:

hydrogen production VIII , photosynthesis light reactions :
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]

methane oxidation to methanol II :
methane + an electron-transfer-related quinol + oxygen → methanol + an electron-transfer-related quinone + H2O

TCA cycle VI (obligate autotrophs) :
succinate[in] + an electron-transfer-related quinone[CCO-OUT-CCO-IN] ← fumarate[in] + an electron-transfer-related quinol[CCO-OUT-CCO-IN]

Not in pathways:
2 an oxidized c-type cytochrome[out] + an electron-transfer-related quinol → 2 a reduced c-type cytochrome[out] + an electron-transfer-related quinone + 2 H+[in]

Reactions known to produce the compound:

hydrogen production VIII , photosynthesis light reactions :
4 hν + 2 a plastoquinone + 2 H2O ↔ 2 a plastoquinol + oxygen

trans-lycopene biosynthesis II (plants) :
15-cis-phytoene + a plastoquinone → 15,9'-di-cis-phytofluene + a plastoquinol
15,9'-di-cis-phytofluene + a plastoquinone → 9,15,9'-tri-cis-ζ-carotene + a plastoquinol

Not in pathways:
2 a plastoquinol[chloroplast thylakoid membrane] + oxygen[chloroplast thylakoid lumen] + 4 H+[chloroplast thylakoid lumen] ← hν + 2 a plastoquinone[chloroplast thylakoid membrane] + 2 H2O[chloroplast thylakoid lumen] + 4 H+[chloroplast stroma]

(5R)-carbapenem carboxylate biosynthesis , citrulline biosynthesis , L-Nδ-acetylornithine biosynthesis , proline degradation :
L-proline + an electron-transfer-related quinone[inner membrane] → (S)-1-pyrroline-5-carboxylate + an electron-transfer-related quinol[inner membrane] + H+

4-hydroxymandelate degradation :
(S)-4-hydroxymandelate + an electron-transfer-related quinone → 2-(4-hydroxyphenyl)-2-oxoacetate + an electron-transfer-related quinol

alanine degradation I :
D-alanine + an electron-transfer-related quinone[inner membrane] + H2O → ammonium + pyruvate + an electron-transfer-related quinol[inner membrane]

sulfide oxidation I (sulfide-quinone reductase) :
hydrogen sulfide + an electron-transfer-related quinone → intracellular S0 + an electron-transfer-related quinol

TCA cycle IV (2-oxoglutarate decarboxylase) , TCA cycle V (2-oxoglutarate:ferredoxin oxidoreductase) , TCA cycle VII (acetate-producers) :
succinate[in] + an electron-transfer-related quinone[CCO-OUT-CCO-IN] → fumarate[in] + an electron-transfer-related quinol[CCO-OUT-CCO-IN]

trans-4-hydroxy-L-proline degradation I :
trans-4-hydroxy-L-proline[in] + an electron-transfer-related quinone → pyrroline-hydroxy-carboxylate[in] + an electron-transfer-related quinol + H+[in]

trans-lycopene biosynthesis II (plants) :
9,9'-di-cis-ζ-carotene + an electron-transfer-related quinone → 7,9,9'-cis-neurosporene + an electron-transfer-related quinol
7,9,9'-cis-neurosporene + an electron-transfer-related quinone → prolycopene + an electron-transfer-related quinol


sn-glycerol 3-phosphate[in] + an electron-transfer-related quinone[CCO-OUT-CCO-IN] → dihydroxyacetone phosphate[in] + an electron-transfer-related quinol[CCO-OUT-CCO-IN]
D-glucopyranose[out] + an electron-transfer-related quinone + 2 H+[in] → D-glucono-1,5-lactone[out] + an electron-transfer-related quinol + 2 H+[out]
a D-amino acid[in] + an electron-transfer-related quinone[CCO-OUT-CCO-IN] + H2O[in] → a 2-oxo carboxylate[in] + ammonium[in] + an electron-transfer-related quinol[CCO-OUT-CCO-IN]
NADPH + an electron-transfer-related quinone + H+ → NADP+ + an electron-transfer-related quinol
(S)-dihydroorotate + an electron-transfer-related quinone[inner membrane] → orotate + an electron-transfer-related quinol[inner membrane]

quinate degradation I :
L-quinate + a quinone → 3-dehydroquinate + a quinol

shikimate degradation I :
shikimate + a quinone → 3-dehydroshikimate + a quinol

TCA cycle I (prokaryotic) , TCA cycle VII (acetate-producers) :
(S)-malate + a quinone → oxaloacetate + a quinol

thiosulfate oxidation II (to tetrathionate) :
2 thiosulfate + a quinone → tetrathionate + a quinol


a cyclic alcohol + a quinone → a cyclic ketone + a quinol
a quinone + NAD(P)H + H+a quinol + NAD(P)+

Reactions known to both consume and produce the compound:

hydrogen production VIII :
a plastoquinone + NAD(P)H + H+a plastoquinol + NAD(P)+

nitrate reduction I (denitrification) , nitrate reduction VII (denitrification) :
nitrate[in] + an electron-transfer-related quinol ↔ nitrite[in] + an electron-transfer-related quinone + H2O[in]

In Reactions of unknown directionality:

Not in pathways:
15-cis-phytoene + 2 a plastoquinone = 9,15,9'-tri-cis-ζ-carotene + 2 a plastoquinol


an oxidized coenzyme F420 + an electron-transfer-related quinol = a reduced coenzyme F420 + an electron-transfer-related quinone
an (R)-2-hydroxyacid + an electron-transfer-related quinone = a 2-oxo acid + an electron-transfer-related quinol
NADH + an electron-transfer-related quinone + H+ = NAD+ + an electron-transfer-related quinol
formate + an electron-transfer-related quinone + H+ = CO2 + an electron-transfer-related quinol
9,9'-di-cis-ζ-carotene + 2 an electron-transfer-related quinone = prolycopene + 2 an electron-transfer-related quinol


1-(β-D-ribofuranosyl)-1,4-dihydronicotinamide + a quinone + H+ = a quinol + 1-(β-D ribofuranosyl)nicotinamide
phenylacetyl-CoA + 2 a quinone + H2O = 2 a quinol + phenylglyoxylyl-CoA

In Redox half-reactions:
a plastoquinone + 4 H+[in] + 2 e-a plastoquinol + 2 H+[out] ,
a plastoquinone + 2 H+[in] + 2 e-a plastoquinol ,
a plastoquinone + 2 H+[out] + 2 e-a plastoquinol ,
an electron-transfer-related quinone + 2 H+[in] + 2 e-an electron-transfer-related quinol

Credits:
Revised 17-Aug-2009 by Caspi R , SRI International


References

Collins81: Collins MD, Jones D (1981). "Distribution of isoprenoid quinone structural types in bacteria and their taxonomic implication." Microbiol Rev 45(2);316-54. PMID: 7022156

Kawamukai02: Kawamukai M (2002). "Biosynthesis, bioproduction and novel roles of ubiquinone." J Biosci Bioeng 94(6);511-7. PMID: 16233343

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Sun Nov 23, 2014, BIOCYC14B.