Precorrin 3B C17 methyltransferase

In enzymology, a precorrin-3B C17-methyltransferase (EC 2.1.1.131) is an enzyme that catalyzes the chemical reaction

Thus, the two substrates of this enzyme are S-adenosyl methionine and precorrin 3B, whereas its two products are S-adenosylhomocysteine and precorrin 4.

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:precorrin-3B C17-methyltransferase. Other names in common use include precorrin-3 methyltransferase, and CobJ. This enzyme participates in porphyrin and chlorophyll metabolism.