|Superclasses:||Reactions Classified By Conversion Type → Simple Reactions → Chemical Reactions|
|Reactions Classified By Substrate → Small-Molecule Reactions|
EC Number: 188.8.131.52
In Pathway: ubiquinol-8 biosynthesis (prokaryotic)
Note that this reaction equation differs from the official Enzyme Commission reaction equations for this EC number.
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.
Most BioCyc compounds have been protonated to a reference pH value of 7.3, and some reactions have been computationally balanced for hydrogen by adding free protons. Please see the PGDB Concepts Guide for more information.
Mass balance status: Balanced.
Enzyme Commission Primary Name: 3-demethylubiquinol 3-O-methyltransferase
Enzyme Commission Synonyms: 5-demethylubiquinone-9 methyltransferase, OMHMB-methyltransferase, 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone methyltransferase, S-adenosyl-L-methionine:2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone-O-methyltransferase, COQ3 (gene name), Coq3 O-methyltransferase, ubiG (gene name, ambiguous)
This is the ninth and final step in ubiquinone biosynthesis.
Enzyme Commission Summary:
This enzyme is involved in ubiquinone biosynthesis. Ubiquinones from different organisms have a different number of prenyl units (for example, ubiquinone-6 in Saccharomyces, ubiquinone-9 in rat and ubiquinone-10 in human), and thus the natural substrate for the enzymes from different organisms has a different number of prenyl units. However, the enzyme usually shows a low degree of specificity regarding the number of prenyl units. For example, the human COQ3 enzyme can restore biosynthesis of ubiquinone-6 in coq3 deletion mutants of yeast [Poon99].
Houser77: Houser RM, Olson RE (1977). "5-demethylubiquinone-9-methyltransferase from rat liver mitochondria. Characterization, localization, and solubilization." J Biol Chem 252(12);4017-21. PMID: 863914
Jonassen00: Jonassen T, Clarke CF (2000). "Isolation and functional expression of human COQ3, a gene encoding a methyltransferase required for ubiquinone biosynthesis." J Biol Chem 275(17);12381-7. PMID: 10777520
Leppik76a: Leppik RA, Stroobant P, Shineberg B, Young IG, Gibson F (1976). "Membrane-associated reactions in ubiquinone biosynthesis. 2-Octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone methyltransferase." Biochim Biophys Acta 1976;428(1);146-56. PMID: 769831
Poon99: Poon WW, Barkovich RJ, Hsu AY, Frankel A, Lee PT, Shepherd JN, Myles DC, Clarke CF (1999). "Yeast and rat Coq3 and Escherichia coli UbiG polypeptides catalyze both O-methyltransferase steps in coenzyme Q biosynthesis." J Biol Chem 274(31);21665-72. PMID: 10419476
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