The invention relates to norcoclaurine synthases and substrate binding sites having one or more site-
specific mutation which increase the activity, when compared to the
wild type synthase, of the condensation of 4-HPAA and
dopamine to (S)-norcoclaurine and / or 3,4-DhPAA and
dopamine to (S)-norlaudanosoline. The inventors both identified specific mutations corresponding to at position 73, 75, 77, 82, 99, 114, 141, 142, 147, 152, 174 and / or 178 in the count according to SEQ ID No: 1, and sites corresponding to the binding domains defined in SEQ IN NO: 4 and 5, where the mutated increase of the activity may be positioned within these norcoclaurine synthases. These domains are conserved regions.