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ENZYME entry: EC

Accepted Name
Polyprenyldihydroxybenzoate methyltransferase.
Alternative Name(s)
3,4-dihydroxy-5-hexaprenylbenzoate methyltransferase.
DHHB methyltransferase.
DHHB O-methyltransferase.
Dihydroxyhexaprenylbenzoate methyltransferase.
Reaction catalysed
S-adenosyl-L-methionine + 3,4-dihydroxy-5-all-trans-polyprenylbenzoate <=> S-adenosyl-L-homocysteine + 3-methoxy-4-hydroxy-5-all-trans-polyprenylbenzoate
  • 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.
  • The enzymes from yeast and rat also catalyze the methylation of 3-demethylubiquinol-6 and 3-demethylubiquinol-9, respectively (this activity is classified as EC
PRIAM enzyme-specific profiles2.1.1.114
KEGG Ligand Database for Enzyme Nomenclature2.1.1.114
IUBMB Enzyme Nomenclature2.1.1.114
MEDLINEFind literature relating to
O49354, COQ3_ARATH;  Q3T131, COQ3_BOVIN;  O93995, COQ3_CANAX;  
Q63159, COQ3_RAT;  O74421, COQ3_SCHPO;  P27680, COQ3_YEAST;  

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