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MetaCyc Compound Class: a menaquinone

Abbrev Name: MQ

Synonyms: a vitamin K2

Superclasses: a redox electron carrier Membrane-Electron-Carriers an electron-transfer quinone
a vitamin a vitamin K
an aldehyde or ketone a ketone a cyclic ketone a quinone an electron-transfer quinone

Summary:
Menaquinones and demethylmenaquinones are isoprenoid quinones of the naphthalene series, and are constituents of bacterial plasma membranes, where they play important roles in electron transfer and oxidative phosphorylation. Menaquinones are the most widespread respiratory quinones in biological system [Fujimoto12]. Menaquinones and demethylmenaquinones are named MK-n or DMK-n, respectively, where the n refers to the number of prenyl units present in the side chain. The most common length of the side chain in bacteria is 8, although minor amounts of MK-1 through MK-14 have been found [Collins81].

Many bacteria and archaea have dehydrogenated menaquinones, which are named MK-n(H2). The degree and location of dehydrogenation depends on the species. Some organisms have menaquinones with modifications of the head group, for example Thermoplasma possess both thermoplasmaquinones (TPQ), which contains an extra methyl group, and methionaquinones (MTK), which contains a methylthio group [Shimada01].

Menaquinones are also known as vitamin K2. Vitamin K is a name given to a group of derivatives of 2-methyl-1,4-naphthoquinone that are required by mammals for the posttranslational modification of certain proteins, mostly involved in blood coagulation. These compounds, while essential for mammals, are not synthesized by them, and are thus considered vitamins.

The natural forms of the vitamin are vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). Since menaquinones produced by different organisms have different tail lengths there are many variations of vitamin K2, usually specified based on the number of carbons in their tails, such as in Vitamin K2(45).

The reduced form of menaquinone is called a menaquinol.

a menaquinone compound structure

Child Classes: a dihidromenaquinone (2) , a modified menaquinone (0)

Instances:
menaquinone-1 ,
menaquinone-2 ,
menaquinone-3 ,
menaquinone-4 ,
menaquinone-5 ,
menaquinone-6 ,
menaquinone-7 ,
menaquinone-8 ,
menaquinone-9 ,
menaquinone-10 ,
menaquinone-11 ,
menaquinone-12 ,
menaquinone-13 ,
methionaquinone-7 ,
thermoplasmaquinone-7

SMILES: CC(C[R])=CCC1(C(C2(C(C(C=1C)=O)=CC=CC=2))=O)

Unification Links: KEGG:C00828

Reactions known to consume the compound:

formate to dimethyl sulfoxide electron transfer , formate to trimethylamine N-oxide electron transfer , nitrate reduction III (dissimilatory) :
formate[periplasmic space] + a menaquinone[inner membrane] + 2 H+ → CO2[periplasmic space] + a menaquinol[inner membrane] + H+[periplasmic space]

heme biosynthesis II (anaerobic) :
protoporphyrin IX[in] + 3 a menaquinol[membrane] ← protoporphyrinogen IX[in] + 3 a menaquinone[membrane]

NADH to dimethyl sulfoxide electron transfer , NADH to fumarate electron transfer , NADH to trimethylamine N-oxide electron transfer , nitrate reduction VIIIa (dissimilatory) :
NADH + a menaquinone[inner membrane] + 5 H+ → NAD+ + a menaquinol[inner membrane] + 4 H+[periplasmic space]

sulfite oxidation V (SoeABC) :
sulfite + a menaquinone + H2O → sulfate + a menaquinol

TCA cycle VIII (helicobacter) :
(S)-malate + a menaquinone → oxaloacetate + a menaquinol

Not in pathways:
NADH[in] + a menaquinone[membrane] + H+[in] → NAD+[in] + a menaquinol[membrane]
sn-glycerol 3-phosphate + a menaquinone[inner membrane] → glycerone phosphate + a menaquinol[inner membrane]
a menaquinone[inner membrane] + 2 H+ + H2[periplasmic space] → a menaquinol[inner membrane] + 2 H+[periplasmic space]
(S)-dihydroorotate + a menaquinone[inner membrane] → orotate + a menaquinol[inner membrane]

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

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

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

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

TCA cycle I (prokaryotic) :
(S)-malate[in] + an electron-transfer quinone[membrane] → oxaloacetate[in] + an electron-transfer quinol[membrane]

TCA cycle IV (2-oxoglutarate decarboxylase) , TCA cycle V (2-oxoglutarate:ferredoxin oxidoreductase) :
succinate[in] + an electron-transfer quinone[membrane] → fumarate[in] + an electron-transfer quinol[membrane]

TCA cycle VII (acetate-producers) :
succinate[in] + an electron-transfer quinone[membrane] → fumarate[in] + an electron-transfer quinol[membrane]
(S)-malate[in] + an electron-transfer quinone[membrane] → oxaloacetate[in] + an electron-transfer quinol[membrane]

trans-4-hydroxy-L-proline degradation I :
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]

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

UMP biosynthesis :
(S)-dihydroorotate + an electron-transfer quinone[inner membrane] → orotate + an electron-transfer quinol[inner membrane]

Not in pathways:
a D-amino acid[in] + an electron-transfer quinone[membrane] + H2O[in] → a 2-oxo carboxylate[in] + ammonium[in] + an electron-transfer quinol[membrane]
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]
sn-glycerol 3-phosphate[in] + an electron-transfer quinone[membrane] → glycerone phosphate[in] + an electron-transfer quinol[membrane]
an electron-transfer quinone[membrane] + NAD(P)H[in] + H+[in] → an electron-transfer quinol[membrane] + NAD(P)+[in]

Reactions known to produce the compound:

formate to trimethylamine N-oxide electron transfer , NADH to trimethylamine N-oxide electron transfer :
trimethylamine N-oxide[periplasmic space] + a menaquinol[inner membrane] + H+[periplasmic space] → trimethylamine[periplasmic space] + a menaquinone[inner membrane] + H2O[periplasmic space]

nitrate reduction III (dissimilatory) , nitrate reduction VIIIa (dissimilatory) :
nitrate + a menaquinol[inner membrane] + 2 H+ → nitrite + a menaquinone[inner membrane] + H2O + 2 H+[periplasmic space]

nitrate reduction VII (denitrification) :
2 nitric oxide[periplasmic space] + a menaquinol[periplasmic space] → nitrous oxide[periplasmic space] + a menaquinone[periplasmic space] + H2O[periplasmic space]

Not in pathways:
S-adenosyl-L-methionine + a demethylmenaquinone → S-adenosyl-L-homocysteine + a menaquinone
2 a menaquinol[membrane] + oxygen[in] + 8 H+[in] → 2 a menaquinone[membrane] + 8 H+[out] + 2 H2O[in]
2 an oxidized c-type cytochrome[out] + a menaquinol[membrane] → 2 a reduced c-type cytochrome[out] + a menaquinone[membrane] + 2 H+[in]

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

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

Not in pathways:
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]

cuticular wax biosynthesis :
a secondary alcohol + an unknown oxidized electron acceptor → a ketone + an unknown reduced electron acceptor

Not in pathways:
a secondary alcohol + oxygen → a ketone + hydrogen peroxide

Not in pathways:
a nitroalkane + oxygen + H2O → an aldehyde or ketone + nitrite + hydrogen peroxide + H+

Reactions known to both consume and produce the compound:

formate to dimethyl sulfoxide electron transfer , NADH to dimethyl sulfoxide electron transfer :
dimethyl sulfide[periplasmic space] + a menaquinone[inner membrane] + H2O[periplasmic space] ← dimethyl sulfoxide[periplasmic space] + a menaquinol[inner membrane]

incomplete reductive TCA cycle , mixed acid fermentation , NADH to fumarate electron transfer , pyruvate fermentation to propanoate I , reductive TCA cycle I , reductive TCA cycle II , TCA cycle VIII (helicobacter) :
fumarate[in] + a menaquinol[membrane] ↔ succinate[in] + a menaquinone[membrane]

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

Not in pathways:
2 a quinone + NADPH + H+ ↔ 2 a semiquinone + NADP+

In Reactions of unknown directionality:

Not in pathways:
a menaquinone + H2 = a menaquinol

Not in pathways:
9,9'-di-cis-ζ-carotene + 2 an electron-transfer quinone = prolycopene + 2 an electron-transfer quinol
formate + an electron-transfer quinone + H+ = CO2 + an electron-transfer quinol
NADH + an electron-transfer quinone + H+ = NAD+ + an electron-transfer quinol
an (R)-2-hydroxyacid + an electron-transfer quinone = a 2-oxo acid + an electron-transfer quinol
an aldehyde + an electron-transfer quinone + H2O = a carboxylate + an electron-transfer quinol + H+
an oxidized coenzyme F420 + an electron-transfer quinol = a reduced coenzyme F420 + an electron-transfer quinone

Not in pathways:
2 a quinone + NADH + H+ = 2 a semiquinone + NAD+
1-(β-D-ribofuranosyl)-1,4-dihydronicotinamide + a quinone + H+ = a quinol + 1-(β-D ribofuranosyl)nicotinamide

Not in pathways:
a ketone + NADP+ = an enone + NADPH + H+
a secondary alcohol + an oxidized coenzyme F420 = a ketone + a reduced coenzyme F420
a secondary alcohol + NADP+ = a ketone + NADPH + H+
a secondary alcohol + NAD+ = a ketone + NADH + H+

In Redox half-reactions:
a menaquinone[membrane] + 2 H+[in] + 2 e-[membrane] → a menaquinol[membrane] ,
a menaquinone[membrane] + 2 H+[out] + 2 e-[membrane] → a menaquinol[membrane] ,
an electron-transfer quinone[membrane] + 2 H+[in] + 2 e-[membrane] → an electron-transfer quinol[membrane]

This compound has been characterized as a cofactor or prosthetic group of the following enzymes: putrescine oxidase

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

Fujimoto12: Fujimoto N., Kosaka T., Yamada M. (2012). "Menaquinone as Well as Ubiquinone as a Crucial Component in the Escherichia coli Respiratory Chain." Chapter 10 in Chemical Biology, edited by D Ekinci, ISBN 978-953-51-0049-2.

Shimada01: Shimada H, Shida Y, Nemoto N, Oshima T, Yamagishi A (2001). "Quinone profiles of Thermoplasma acidophilum HO-62." J Bacteriol 183(4);1462-5. PMID: 11157962


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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
Page generated by SRI International Pathway Tools version 19.0 on Fri May 22, 2015, BIOCYC14B.