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MetaCyc Reaction: 2.1.1.64

Superclasses: Reactions Classified By Conversion Type Simple Reactions Chemical Reactions
Reactions Classified By Substrate Small-Molecule Reactions

EC Number: 2.1.1.64

Enzymes and Genes:
hexaprenyldihydroxybenzoate methyltransferase Inferred from experiment : COQ3 ( Homo sapiens )

In Pathway: ubiquinol-10 biosynthesis (prokaryotic) , ubiquinol-10 biosynthesis (eukaryotic)

Note that this reaction equation differs from the official Enzyme Commission reaction equation for this EC number, which can be found here .

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

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.

Direct generic reaction:
S-adenosyl-L-methionine + a demethylated ubiquinol → S-adenosyl-L-homocysteine + an ubiquinol + H+ (2.1.1.64)

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)

Standard Gibbs Free Energy (ΔrG in kcal/mol): -4.3598633 Inferred by computational analysis [Latendresse13]

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].

The enzymes from yeast, Escherichia coli and rat also catalyse the methylation of 3,4-dihydroxy-5-all-trans-polyprenylbenzoate [Poon99] (this reaction is classified as EC 2.1.1.114).

Citations: [Houser77, Leppik76, Jonassen00]

Gene-Reaction Schematic: ?

Instance reactions of [a 3-(all-trans-polyrenyl)benzene-1,2-diol + S-adenosyl-L-methionine → a 2-methoxy-6-(all-trans-polyprenyl)phenol + S-adenosyl-L-homocysteine + H+] (2.1.1.222):
i1: 3-(all-trans-decaprenyl)benzene-1,2-diol + S-adenosyl-L-methionine → 2-methoxy-6-(all-trans-decaprenyl)phenol + S-adenosyl-L-homocysteine + H+ (2.1.1.222)

i2: 3-(all-trans-nonaprenyl)benzene-1,2-diol + S-adenosyl-L-methionine → 2-methoxy-6-(all-trans-nonaprenyl)phenol + S-adenosyl-L-homocysteine + H+ (2.1.1.222)

i3: 3-(all-trans-octaprenyl)benzene-1,2-diol + S-adenosyl-L-methionine → 2-methoxy-6-(all-trans-octaprenyl)phenol + S-adenosyl-L-homocysteine + H+ (2.1.1.222)

i4: 3-(all-trans-heptaprenyl)benzene-1,2-diol + S-adenosyl-L-methionine → 2-methoxy-6-(all-trans-heptaprenyl)phenol + S-adenosyl-L-homocysteine + H+ (2.1.1.222)

Relationship Links: BRENDA:EC:2.1.1.64 , ENZYME:EC:2.1.1.64 , IUBMB-ExplorEnz:EC:2.1.1.64

Credits:
Revised 11-Oct-2010 by Caspi R , SRI International


References

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

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Leppik76: 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


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Thu Nov 20, 2014, BIOCYC14B.