[Prenylquinones--occurrence, biosynthesis and functions]

Prenylquinones are a group of compounds occurring in all living cells. In their structure a polar head group undergoing redox reactions and a long, hydrophobic side-chain can be found. Due to their amphiphilic character, these compounds are mainly located in biological membranes where they function as electron and proton carriers in the photosynthetic and respiratory electron transport chains. Prenylquinones play also additional roles such as antioxidants, and other more specific functions such as enzyme cofactors. Based on the ring structure, different groups of prenylquinones are distinguished: menaquinones, phylloquinone, ubiquinones and plastoquinones, although also other representatives of this group are known, e.g. tocopherolquinones. Frequently, biosynthesis ability of a given kind of prenylquinones is limited to a certain group of organisms. This review describes the structure, function and biosynthesis of most common prenylquinones.