In enzymology, tetrahydrocolumbamine 2-O-methyltransferase () is an enzyme that catalyzes the chemical reaction:
In this methylation reaction, the enzyme uses the cofactor, S-adenosyl methionine (SAM) which transfers a methyl group, giving S-adenosyl-L-homocysteine (SAH) as a by-product. There are several similar transformations in the chemistry of isoquinoline alkaloids.
This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:5,8,13,13a-tetrahydrocolumbamine 2-O-methyltransferase. This enzyme is also called tetrahydrocolumbamine methyltransferase. This enzyme participates in alkaloid biosynthesis.