Isotopically Sensitive Branching as a Tool for Evaluating Multiple Product Formation by Monoterpene Cyclases

Article abstract of DOI:10.1016/S0040-4020(01)86486-3

The deuterated substrates <4-2H2,1-3H>geranyl pyrophosphate and <10-2H3,1-3H>geranyl pyrophosphate were employed to examine isotopically sensitive branching in the biosynthesis of monoterpene olefin isomers.By this method, (-)-α-pinene and (-)-β-pinene were shown to be synthesized via a common intermediate by a single cyclization enzyme from grand fir (Abies grandis), as were (-)-α-phellandrene and (-)-β-phellandrene by a single cyclase from lodgepole pine (Pinus contorta).Kinetic isotope effects were determined for the various deprotonations leading to the pinenes and phellandrenes.Key Words: Isotopically sensitive branching, monoterpene biosynthesis, monoterpene cyclase, resin biosynthesis, kinetic isotope effect.