Biosynthesis, bioproduction and novel roles of ubiquinone.

Ubiquinone (coenzyme Q) is a well-known component of the electron transfer system in living organisms. It is known that ubiquinone transfers electrons from Complex I (or Complex II) to Complex III in the respiratory chain. However, recent evidence indicates that an involvement in respiration is not the sole role of ubiquinone, and various novel roles have been elucidated. A role as a lipid soluble antioxidant is now widely accepted. The relationship between lifespan and ubiquinone has attracted much interest based on the study of a Caenorhabditis elegans clk-1 mutant. The connection between disulfide bond formation and ubiquinone (or menaquinone) in Escherichia coli has been well studied. The production of hydrogen sulfide in a ubiquinone-deficient fission yeast is an interesting phenotype recently observed. These are some examples of the novel roles of ubiquinone and this review summarizes the recent findings relating to the biosynthesis, bioproduction and novel roles of ubiquinone.