2.1.1.153 7-O-methylvitexin competitive inhibition 2.1.1.153 7-O-methylvitexin 2''-O-beta-L-rhamnoside product inhibition, kinetics 2.1.1.153 additional information not inhibited by Mg2+ or 2-mercaptoethanol 2.1.1.153 S-adenosyl-L-homocysteine strong product inhibition, kinetics 2.1.1.153 vitexin competitive inhibition