InterPro domain: IPR010971

This entry represents a family of FAD-dependent hydroxylases (monooxygenases), which are all believed to act in the aerobic ubiquinone biosynthesis pathway [ 1 ]. In Escherichia coli, three enzyme activities have been described: UbiI, UbiH and UbiF [ 2 ]. UbiH and UbiF are similar to one another and form the basis of this subfamily. UbiI (also known as visC) [ 3 ] is highly similar to UbiF, adjacent to UbiH and, when mutated, results in a phenotype similar to that of UbiH (also known as visB) [ 3 ]. Several other species appear to have three homologues in this family, although they assort themselves differently on phylogenetic trees (e.g. Xylella and Mesorhizobium) making it difficult to ascribe a specific activity to each one. Eukaryotes appear to have only a single homologue in this subfamily (COQ6, [ 4 ]) which complements UbiH, but also possess a non-orthologous gene, COQ7 which complements UbiF.

1. Ubiquinone biosynthesis in microorganisms. FEMS Microbiol. Lett. 203, 131-9
2. ubiI, a new gene in Escherichia coli coenzyme Q biosynthesis, is involved in aerobic C5-hydroxylation. J. Biol. Chem. 288, 20085-92
3. Isolation and characterization of a light-sensitive mutant of Escherichia coli K-12 with a mutation in a gene that is required for the biosynthesis of ubiquinone. J. Bacteriol. 174, 7352-9
4. The Saccharomyces cerevisiae COQ6 gene encodes a mitochondrial flavin-dependent monooxygenase required for coenzyme Q biosynthesis. J. Biol. Chem. 278, 25308-16