MSI_000046525

Ubiquinone-4 is a member of the chemical class known as Polyprenylbenzoquinones. These are compounds containing a polyisoprene chain attached to a quinone at the second ring position. Ubiquione-4 has just 4 isoprene units. Normally in humans it has 10 (CoQ10). Ubiquinone-4 is an intermediate in the synthesis of Ubiquionone 10. Ubiquinone-4 is a Coenzyme Q analogue that have been identified in brain. Based on the isoprenoid moiety, the presence of various coenzyme Q homologues in prokaryotes and eurkaryotes has been confirmed, and these homologues are classified as Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, and Q12. The numbers, Qn, refer to the number of isoprenoid units attached at the 6- position on the benzoquinone ring of the coenzyme Q moiety. (PMID: 12064350) Coenzyme Q is the only type of Quinone naturally found in animals (other quinones such as vitamin K is provided by foods). Coenzyme Q is a fat-soluble and amphipathic compound that is the integral component of the electron transport chain in mitochondria. It is ubiquitous in nature and is found in subcellular organelles, serum lipoproteins, blood plasma, urine, and feces. Ubiquinones are amphipathic because of the benzoquinone ring (hydrophilic) and the polyisoprenoid side chain moiety (lipophilic). The primary role of coenzyme Q is to transfer electrons between redox components of the electron transport chain, to create a proton gradient across the inner mitochondrial membrane and drive ATP formation. Additional functions of coenzyme Q are to influence membrane fluidity; to recycle the radical forms of vitamin C and E; and, most important, to act as a lipid antioxidant protecting membrane phospholipids against peroxidation. Coenzyme Q is the only endogenously occurring lipid-soluble antioxidant that occurs ubiquitously and can be synthesized in all organisms. Isolated from various yeasts