Precorrin-3B C17-methyltransferase

In enzymology, precorrin-3B C17-methyltransferase is an enzyme that catalyzes the chemical reaction


 * S-adenosyl-L-methionine + precorrin-3B $$\rightleftharpoons$$ S-adenosyl-L-homocysteine + precorrin-4
 * Precorrin-3B to Precorrin-4.svg

The two substrates of this enzyme are S-adenosyl methionine and precorrin 3B, and 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 is part of the biosynthetic pathway to cobalamin (vitamin B12) in aerobic bacteria and during this step the macrocycle ring-contracts so that the corrin core of the vitamin is formed.