Molecular function

2-polyprenyl-6-methoxy-1,4-benzoquinone methylase activity, coenzyme Q biosynthesis methyltransferase activity, coenzyme Q biosynthetic process methyltransferase activity

Catalysis of the reaction: 2-polyprenyl-6-methoxy-1,4-benzoquinone + S-adenosyl-L-methionine = 2-polyprenyl-3-methyl-6-methoxy-1,4-benzoquinone + S-adenosyl-L-homocysteine.

Note that the polyprenyl sidechain substrate for this reaction has a different number of prenyl units in different organisms (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.