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Escherichia coli K-12 substr. MG1655 Compound Class: a menaquinone

Abbrev Name: MQ

Synonyms: a vitamin K2

Superclasses: a vitamin a vitamin K
an acceptor a redox electron carrier Membrane-Electron-Carriers an electron-transfer quinone
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 systems [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 dihydromenaquinone (0) , a modified menaquinone (0)

Instances:
menaquinone-1 ,
menaquinone-8

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 nitrite 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]

glycerol degradation I , glycerol-3-phosphate to fumarate electron transfer , glycerophosphodiester degradation , nitrate reduction IX (dissimilatory) :
sn-glycerol 3-phosphate + a menaquinone[inner membrane] → glycerone phosphate + a menaquinol[inner membrane]

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

hydrogen to dimethyl sulfoxide electron transfer , hydrogen to fumarate electron transfer , hydrogen to trimethylamine N-oxide electron transfer :
a menaquinone[inner membrane] + 2 H+ + H2[periplasmic space] → a menaquinol[inner membrane] + 2 H+[periplasmic space]

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

Not in pathways:
NADH + a menaquinone[inner membrane] + H+ → NAD+ + a menaquinol[inner membrane]
(S)-dihydroorotate + a menaquinone[inner membrane] → orotate + a menaquinol[inner membrane]

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

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

Not in pathways:
a D-amino acid + an electron-transfer quinone[inner membrane] + H2O → ammonium + a 2-oxo carboxylate + an electron-transfer quinol[inner membrane]
(S)-dihydroorotate + an electron-transfer quinone[inner membrane] → orotate + an electron-transfer quinol[inner membrane]
NADPH + an electron-transfer quinone[inner membrane] + H+ → NADP+ + an electron-transfer quinol[inner membrane]
an electron-transfer quinone[inner membrane] + NAD(P)H + H+ → an electron-transfer quinol[inner membrane] + NAD(P)+

Reactions known to produce the compound:

formate to nitrite electron transfer :
nitrite[periplasmic space] + 3 a menaquinol[inner membrane] + 2 H+[periplasmic space] → ammonium[periplasmic space] + 3 a menaquinone[inner membrane] + 2 H2O[periplasmic space]

formate to trimethylamine N-oxide electron transfer , hydrogen 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 IX (dissimilatory) , nitrate reduction VIII (dissimilatory) :
nitrate + a menaquinol[inner membrane] + 2 H+ → nitrite + a menaquinone[inner membrane] + H2O + 2 H+[periplasmic space]

Not in pathways:
nitrate[periplasmic space] + a menaquinol[inner membrane] → nitrite[periplasmic space] + a menaquinone[inner membrane] + H2O[periplasmic space]

Reactions known to both consume and produce the compound:

formate to dimethyl sulfoxide electron transfer , hydrogen 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]

glycerol-3-phosphate to fumarate electron transfer , hydrogen to fumarate electron transfer , mixed acid fermentation , NADH to fumarate electron transfer :
fumarate + a menaquinol[inner membrane] ↔ succinate + a menaquinone[inner membrane]

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

In Reactions of unknown directionality:

Not in pathways:
2 a quinone + NADH + H+ = 2 a semiquinone + NAD+

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]

Inhibits: ArcB + ATP → ArcB-Phis292 + ADP


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 EcoCyc: Nucleic Acids Research 41:D605-12 2013
Page generated by SRI International Pathway Tools version 19.0 on Fri Sep 4, 2015, biocyc14.