Ubiquinone


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Ubiquinone

 

(also benzoquinone, coenzyme Q), any of a series of derivatives of 5-methyl-2,3-dimethoxyquinone having a variable terpenoid side chain attached to the carbon atom in position six. Ubiquinones have from six to ten isoprenoid units (C5H8). The structural formula is

Ubiquinones figure in reactions that supply energy to cells. They are designated by the symbols UQn or CoQn; in the first, n represents the number of carbon atoms, and in the second, the number of isoprenoid units. For example, UQ30 will correspond to CoQ6. Ubiquinones occur as colorless, crystalline substances whose absorption maximum is at 270 micrometers. They are insoluble in water and soluble in organic solvents.

Ubiquinones are present in all organisms; UQ50 predominates in mammals, UQ30–50 in fungi, UQ40 in bacteria, UQ40–45 in protozoa, and UQ45–50 in insects. Plant mitochondria contain UQ40–50 in small quantities, and the chloroplasts in plants contain plastoquinones, which are similar to ubiquinones. Various naph-thoquinones occur in certain bacteria.

The biological role of ubiquinones is based on their ability to participate in reversible oxidation-reduction conversions. Ubiquinones are located in the cytoplasmic membranes of bacteria and in the inner membranes of mitochondria. They participate in the transfer of electrons and hydrogen between flavoproteins and cytochrome b in the respiratory chain.

REFERENCES

Skulachev, V. P. Transformatsiia energii v biomembranakh. Moscow, 1972.
Morton, R. A. “Ubiquinones, Plastoquinones, and Vitamins K.” Biological Reviews of the Cambridge Philosophical Society, 1971, vol. 46, no. 1.

V. V. ZUEVSKII

References in periodicals archive ?
Mutations in COQ6 , which is required for the biosynthesis of CoQ10, were first reported in human patients with steroid-resistant FSGS in 2011.[8] CoQ10, also known as ubiquinone, is a lipid-soluble component of virtually all cell membranes, in which CoQ10 is thought to play a crucial antioxidant role and to transport electrons from complexes I and II to complex III in the respiratory chain of the mitochondrial inner membrane.[34] CoQ10 also serves as a lipid-soluble antioxidant and protector against ROS-mediated cell damage.[35] The biochemical pathway of CoQ10 biosynthesis is complex and has not been completely elucidated.
Coulter et al., "Selective targeting of a redox-active ubiquinone to mitochondria within cells: Antioxidant and antiapoptotic properties," The Journal of Biological Chemistry, vol.
The key role of ubiquinone in CAD has been accepted by several researchers extensively.
Decreased ubiquinol levels are often accompanied by increased ubiquinone levels, suggesting that there is an ineffective conversion between ubiquinone and ubiquinol.
The function of mtGPDH has largely been discussed in mammals and invertebrates such as the fruit fly Drosophda melanogaster; the enzyme may act as part of the mitochondrial electron transport chain by transferring electrons to ubiquinone and acting as an uncoupling mechanism susceptible to proton leak (Miwa et al.
TCDD decreases ATP levels and increases reactive oxygen production through changes in mitochondrial [F.sub.0][F.sub.1]-ATP synthase and ubiquinone. Toxicol Applied Pharmacol 217(3):363-374, https://doi.org/10.1016/jTaap.2006.09.014.
Stigmatellin is one of the most potent inhibitors of the ubiquinol oxidation site (Qo site) of complex-III [20], although some chromones have also shown interesting activities on NADH: ubiquinone reductase (complex I) [21, 22].
Under the care of a licensed veterinarian, this dog was entered into our research protocol employing high dose oral DHEA (60 mg/kg/day) and ubiquinone (0.1 mg/kg/day), in divided daily doses.
A series of electron carriers that are evolutionarily conserved conduct electrons derived from the initial oxidation of NADH through a series of iron-sulfur centers to eventually reduce ubiquinone by a mechanism that pumps protons from the mitochondrial matrix to escape to the outside of the mitochondrial membrane.
Ubiquinone (Coenzyme Q10) is required for the inner mitochondrial enzymes used during ATP production where the oxidative phosphorylation process occurs within a cell.
For complexes CII and CIII are involved in the ubiquinone cycle and their binding sites exchange electrons to reduce or oxidize the ubiquinone metabolites.
Co Q10 also known as Ubiquinone was first discovered in the mitochondrial respiratory chain8.