In previous work, some of the variants had moderately higher activity towards resveratrol, and much higher activity towards the intermediate pinostilbene compared to the wild-type, which resulted in a much higher overall activity in the two consecutive O-methylations leading from resveratrol to pterostilbene. As expected, the activity of VvROMT and its variants towards the different p-hydroxycinnamic acids was very low. In biotransformations of p-coumaric acid 1a and caffeic acid 1b by wild-type VvROMT and the seven variants, neither substrate consumption nor product formation was observed (Figure ). For 1b, this means that neither of the two catecholic hydroxy groups could be methylated.