The complex chemistry underlying the extensive transformations involved in terpene indole alkaloid synthesis makes identification of the biosynthetic genes challenging. The present invention relates to methods for producing a terpene indole alkaloid derivative, comprising the steps of: (1) providing a terpene indole alkaloid; and (2) providing a first enzyme termed “Precondylocarpine Acetate Synthase” (PAS) or a functional variant or homologue thereof; and/or a second enzyme termed “Dehydroprecondylocarpine Acetate Synthase” (DPAS) or a functional variant or homologue thereof, and optionally providing further identified enzymes involved in this pathway. The invention also encompasses related kits, enzymes, expression vectors, host cells and plants.