This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: ubiquinone-7 biosynthesis (eukaryotic)
|Superclasses:||Biosynthesis → Cofactors, Prosthetic Groups, Electron Carriers Biosynthesis → Quinol and Quinone Biosynthesis → Ubiquinol Biosynthesis|
Some taxa known to possess this pathway include : Ambrosiozyma llanquihuensis , Barnettozyma californica , Candida berthetii , Candida boidinii , Candida cariosilignicola , Candida dendrica , Candida diversa , Candida ethanolica , Candida freyschussii , Candida inconspicua , Candida maris , Candida maritima , Candida methanolovescens , Candida methanosorbosa , Candida montana , Candida nanaspora , Candida nemodendra , Candida nitratophila , Candida norvegica , Candida odintsovae , Candida ovalis , Candida pignaliae , Candida pini , Candida pseudolambica , Candida quercuum , Candida rugopelliculosa , Candida silvae , Candida silvicultrix , Candida solani , Candida sonorensis , Candida sorboxylosa , Candida stellimalicola , Candida succiphila , Candida vartiovaarae , Candida vini , Cyberlindnera jadinii , Cyberlindnera saturnus , Nakazawaea peltata , Nakazawaea wickerhamii , Ogataea methanolica , Ogataea salicorniae , Phaffomyces opuntiae , Pichia norvegensis , Starmera amethionina , Starmera caribaea , Wickerhamomyces anomalus , Wickerhamomyces mucosus , Williopsis pratensis
Expected Taxonomic Range: Fungi
Ubiquinone (also known as coenzyme Q) is an isoprenoid quinone that functions as an electron carrier in membranes. In eukaryotes ubiquinone is found mostly within the inner mitochondrial membrane, where it functions in respiratory electron transport, transferring two electrons from either complex I (NADH dehydrogenase) or complex II (succinate-ubiquinone reductase) to complex III (bc1 complex). The quinone nucleus of ubiquinone is derived directly from 4-hydroxybenzoate, while the isoprenoid subunits of the polyisoprenoid tail are synthesized via the methylerythritol phosphate pathway I, which feeds isoprene units into the Polyprenyl Biosynthesis pathways.
The number of isoprenoid subunits in the ubiquinone side chain vary in different species. For example, Saccharomyces cerevisiae has 6 such subunits, Escherichia coli K-12 has 8, rat and mouse have 9, and Homo sapiens has 10. The ubiquinones are often named according to the number of carbons in the side chain (e.g. ubi-30) or the number of isoprenoid subunits (e.g. Q-10).
Following addition of the polyprenyl tail, the product (4-hydroxy-3-polyprenylbenzoate), is processed in three steps, namely decarboxylation, oxidation, and methylation. The prokaryotic and eukaryotic pathways differ in the order of these steps: in eukaryotes the compound is oxidized and methylated prior to decarboxylation; in prokaryotes the compound is first decarboxylated, followed by oxidation and methylation [Shepherd96].
The ubiquinone biosynthesis pathway has been elucidated primarily by the use of mutant strains that accumulate pathway intermediates; some of the enzymes in this pathway have not been biochemically characterized.
About This Pathway
ubiquinone-7 (Q-7) is common in yeast. Many strains of Candida, Pichia and Williopsis form Q-7 [Lester59]. As a matter of fact, ubiquinone tail length has been used for the phylogenetic classification of these organisms [Suzuki98b, Suzuki02a]. Q-7 is much less abundant among bacteria (see ubiquinol-7 biosynthesis (prokaryotic)).
Shepherd96: Shepherd, J. A., Poon, W. W., Myles, D. C., Clarke, C. F. (1996). "The biosynthesis of ubiquinone: synthesis and enzymatic modification of biosynthetic precursors." Tetrahedron Lett. 37(14):2395-2398.
Suzuki02a: Suzuki M, Nakase T (2002). "A phylogenetic study of ubiquinone-7 species of the genus Candida based on 18S ribosomal DNA sequence divergence." J Gen Appl Microbiol 48(1);55-65. PMID: 12469316
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