Erythromycin 3''-O-methyltransferase

 Erythromycin 3-O-methyltransferase  (, EryG) is an enzyme with systematic name  S-adenosyl-L-methionine:erythromycin C 3-O-methyltransferase . This enzyme catalyses the following chemical reaction


 * (1) S-adenosyl-L-methionine + erythromycin C $$\rightleftharpoons$$ S-adenosyl-L-homocysteine + erythromycin A
 * (2) S-adenosyl-L-methionine + erythromycin D $$\rightleftharpoons$$ S-adenosyl-L-homocysteine + erythromycin B

The enzyme methylates the 3 position of the mycarosyl moiety of erythromycin C.