Coenzyme Q: Encyclopedia - Coenzyme Q

Coenzyme Q

Coenzyme Q (CoQ), also known as ubiquinone or ubiquinol, is a biologically active quinone with an isoprenoid side chain, related in structure to vitamin K and vitamin E.

Coenzyme Q - History

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

Coenzyme Q - Chemical properties

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.

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

Coenzyme Q - Biochemical role

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 reductase:

Coenzyme Q - Supplementation

Because of its ability to transfer electrons and therefore act as an antioxidant, Coenzyme Q has become a fashionable dietary supplement.

Young people are able to make Q10 from the lower numbered ubiquinones such as Q6 or Q8. The sick and elderly may not be able to make enough. Q10 thus 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 migraines, 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 suggested that Coenzyme Q10 may act as an important antioxidant in the body and the brain. Some of these studies have indicated that Coenzyme Q10 may protect the brain from neurodegenerative disease such as Parkinsons and also from the damaging side effects of a transient ischemic attack (stroke) in the brain.

There has also been a recent study showing a survival benefit after cardiac arrest if coenzyme Q10 is administered in addition to commencing active cooling (to 32–34 degrees Celsius).

Coenzyme Q - Synthesis and Its Inhibition by Statins

The isoprene sidechain of Coenzyme Q10 is synthesized from acetyl CoA by a series of enzymatic reactions, while the benzoquinone portion is synthesized from amino acids.

Coenzyme Q10 shares a common biosynthetic pathway with cholesterol. Isopentenyl pyrophosphate and its isomer, dimethylallyl pyrophosphate, are linked alternatingly in polyprenyl chains, which are also called isoprenes. The 15-carbon isoprene chain is farnesyl pyrophosphate, which is a precursor to cholesterol, while the 50-carbon isoprene chain forms the sidechain of coenzyme Q10.

The synthesis of an intermediary precursor of Coenzyme Q10, mevalonate, is inhibited by statins, a class of cholesterol lowering drugs. [1] Statins can reduce serum levels of coenzyme Q10 by up to 40%.[2]

Adapted from the Wikipedia article "Coenzyme Q", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki