Terpene cyclases are responsible: for the initial cyclization cascade in the multistep synthesis of more than 60 000 known natural products. This abundance of compounds is generated using a very limited pool of substrates based on linear isoprenoids. The astounding 1 diversity obtained. by terpene cyclases suggests a tremendous,catalytic I. challenge to these often promiscuous enzymes. In the current study we present a detailed mechanistic view of the biosynthesis of the monoterpene bornyl diphosphate,(BPP) from geranyl diphosphate by BPP, synthase. state of the art, simulation Methods. We identify the bornyl :cation:as:an enzyme-induced bifurcation, point on the multidimensional. free renergy surface; connecting between the product BPP and the side product camphene:: Chemical dynamics simulations suggest that the active site diphosphate: moiety Steers reaction trajectories toivard. product :formation. Nonetheless; chemical dynamics is not precise enough for exclusive product formation, providing a rationale for the lack Of fidelity in this promiscuous terpene cyclase;