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Coenzyme Q₁₀ (also known as ubiquinone, ubidecarenone, vitamin Q₁₀ or, CoQ₁₀) is a benzoquinone compound synthesised by human and animal tissues. The "Q" and the "10" in the name refer to the quinone chemical group and the 10 isoprenyl chemical subunits, respectively, that are part of this compound's structure.

Contents 1 History 2 Chemical properties 3 Biochemical role 4 Supplementation 5 Biosynthesis 6 Inhibition by statins and beta blockers 7 References 8 External links

Coenzyme Q was first discovered by professor Fred L. Crane and colleagues at the University of Wisconsin-Madison Enzyme Institute in 1957.^[1][2] In 1958, its chemical structure was reported by Dr. D.E. Wolf^[3] and a research group at Merck Laboratories led by Dr. Karl Folkers.^[2]

The oxidized structure of CoQ, or Q, is given here:

The various kinds of Coenzyme Q can be distinguished by the number of isoprenoid side chains they have. The most common CoQ in human mitochondria is Q₁₀. The image above has three isoprenoid units and would be called Q₃.

If Coenzyme Q is reduced by one equivalent, the following structure results, a ubisemiquinone, and is denoted QH. Note the free radical on one of the ring oxygens (either oxygen may become a free radical, in this case the top oxygen is shown as such).

If Coenzyme Q is reduced by two equivalents, the compound becomes a ubiquinol, denoted QH₂:

CoQ is found in the membranes of endoplasmic reticulum, peroxisomes, lysosomes, vesicles and notably the inner membrane of the mitochondrion where it is an important part of the electron transport chain; there it passes reducing equivalents to acceptors such as Coenzyme Q : cytochrome c - oxidoreductase:

CoQH₂+ 2 Fe^III-cytochrome c → CoQ + 2 Fe^II-cytochrome c

CoQ is also essential in the formation of the apoptosome along with other adapter proteins. The loss of trophic factors activates pro-apoptotic enzymes, causing the breakdown of mitochondria.

Because of its ability to transfer electrons and therefore act as an antioxidant, Coenzyme Q has become a valued dietary supplement. CoQ₁₀ has been widely used for the treatment of heart disease (especially heart failure), gum diseases, and also breast cancer.^{[citation needed]} Young people are able to make Q₁₀ from the lower numbered ubiquinones such as Q₆ or Q₈.^{[citation needed]} The sick and elderly may not be able to make enough, thus Q₁₀ becomes a vitamin later in life and in illness.

Supplementation of Coenzyme Q₁₀ has been found to have a beneficial effect on the condition of some sufferers of migraine headaches,^[4] and is a common component of the "mito cocktail" used to treat mitochondrial disorders and other metabolic disorders. It is also being investigated as a treatment for cancer, and as relief from cancer treatment side effects.

Recent studies have shown that the antioxidant properties of Coenzyme Q₁₀ benefit the body and the brain in animal models.^[5][6] Some of these studies indicate that Coenzyme Q₁₀ protects the brain from neurodegenerative disease such as Parkinsons^[7] and also from the damaging side effects of a transient ischemic attack (stroke)^[8] in the brain. Another recent study shows a survival benefit after cardiac arrest if coenzyme Q₁₀ is administered in addition to commencing active cooling (to 32–34 degrees Celsius).^[9]

The benzoquinone portion of Coenzyme Q₁₀ is synthesized from amino acids, while the isoprene sidechain is synthesized from acetyl CoA through the mevalonate pathway. The mevalonate pathway is used for the first steps of cholesterol biosynthesis.

Coenzyme Q₁₀ shares a common biosynthetic pathway with cholesterol. The synthesis of an intermediary precursor of Coenzyme Q₁₀, mevalonate, is inhibited by some beta blockers, blood pressure lowering medication,^[10] and statins, a class of cholesterol lowering drugs.^[11] Statins can reduce serum levels of coenzyme Q₁₀ by up to 40%.^[12] Some research suggests the logical option of supplementation with coenzyme Q₁₀ as a routine adjunct to any treatment which may reduce endogenous production of coenzyme Q₁₀, based on a balance of likely benefit against very small risk.^[13][14]

• An Introduction to Coenzyme Q₁₀ at washington.edu
• Possible Health Benefits of Coenzyme Q₁₀ at oregonstate.edu
• Matthews R, Yang L, Browne S, Baik M, Beal M (1998). "Coenzyme Q10 administration increases brain mitochondrial concentrations and exerts neuroprotective effects". Proc Natl Acad Sci U S A 95 (15): 8892-7. PMID 9671775. 
• Study Suggests Coenzyme Q₁₀ Slows Functional Decline in Parkinson's Disease at ninds.nih.gov
• Grieb P, Ryba M, Sawicki J, Chrapusta S (1997). "Oral coenzyme Q10 administration prevents the development of ischemic brain lesions in a rabbit model of symptomatic vasospasm". Acta Neuropathol (Berl) 94 (4): 363-8. PMID 9341938.