New advances in coenzyme Q biosynthesis

Coenzyme Q (or ubiquinone) is the product of two distinct biosynthetic pathways: the lipid "tail" of coenzyme Q is formed via the isoprene biosynthetic pathway, and the quinone ring derives from the metabolism of either shikimic acid or tyrosine. In general, eukaryotic organisms use the classical mevalonate pathway to form isopentenyl- and dimethylallyl-diphosphate, the five carbon building blocks of the polyisoprenoid tail, and prokaryotes use 1-deoxy-D-xylulose-5-phosphate, formed via the Rohmer pathway. The quinone ring precursor is 4-hydroxybenzoic acid, which is formed directly from chorismate in Saccharomyces cerevisiae and Escherichia coli, or from tyrosine in animal cells. Ring modification steps including prenylation, decarboxylation, and successive hydroxylation and methylation steps form the fully substituted benzoquinone ring of coenzyme Q. Many of the genes and polypeptides involved in coenzyme Q biosynthesis have been isolated and characterized by utilizing strains of E. coli and S. cerevisiae with mutations in the nbi and COQ genes, respectively. This article reviews recent progress in characterizing the biosynthesis of coenzyme Q in E. coli. S. cerevisiae, and other eukaryotic organisms.