Coenzyme Q is well defined as a crucial component of the oxidative phosphorylation process in mitochondria which converts the energy in
carbohydrates and
fatty acids into
ATP to drive cellular machinery and synthesis. New roles for
coenzyme Q in other cellular functions are only becoming recognized. The new aspects have developed from the recognition that
coenzyme Q can undergo oxidation/reduction reactions in other cell membranes such as lysosomes. Golgi or plasma membranes. In mitochondria and lysosomes,
coenzyme Q undergoes reduction/oxidation cycles during which it transfers
protons across the membrane to form a
proton gradient. The presence of high concentrations of
quinol in all membranes provides a basis for
antioxidant action either by direct reaction with radicals or by regeneration of
tocopherol and ascorbate. Evidence for a function in redox control of cell signaling and gene expression is developing from studies on
coenzyme Q stimulation of cell growth, inhibition of apoptosis, control of
thiol groups, formation of
hydrogen peroxide and control of
membrane channels. Deficiency of
coenzyme Q has been described based on failure of biosynthesis caused by gene mutation, inhibition of biosynthesis by
HMG coA reductase inhibitors (
statins) or for unknown reasons in ageing and
cancer. Correction of deficiency requires supplementation with higher levels of
coenzyme Q than are available in the diet.