Erythromycin 3'' O methyltransferase

Erythromycin 3-O-methyltransferase (EC 2.1.1.254, 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 ⇌ S-adenosyl-L-homocysteine + erythromycin A(2) S-adenosyl-L-methionine + erythromycin D ⇌ S-adenosyl-L-homocysteine + erythromycin B

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