Reaction catalyzed by gibberellin A9 O-methyltransferase (2.1.1.275), gibberellin A4 carboxyl methyltransferase (2.1.1.276)
+
=
+
S-adenosyl-L-methionine
+
gibberellin A20
=
S-adenosyl-L-homocysteine
+
methyl gibberellin A20