Nature Catalysis, Published online: 31 July 2026; doi:10.1038/s41929-026-01587-8 Small catalytic nucleophiles can promote allylic transfer processes, but achieving regio- and stereocontrol is challenging. Here the authors develop a family of allylic transferase enzymes to mediate diverse C–C and C–N bond formations through the confinement of key intermediates within proteins.