emodin + S-adenosyl-L-methionine = questin + S-adenosyl-L-homocysteine + H(+)
emodin + s-adenosyl-l-methionine = questin + s-adenosyl-l-homocysteine + h(+)
emodin + S-adenosyl-L-methionine = questin + S-adenosyl-L-homocysteine + H(+)
emodin + s-adenosyl-l-methionine = questin + s-adenosyl-l-homocysteine + h(+)