Functional Switch and Ethyl Group Formation in the Bacterial Polytrichastrene Synthase from Chryseobacterium polytrichastri

A reinvestigation of the linalool synthase from Chryseobacterium polytrichastri uncovered its diterpene synthase activity, yielding polytrichastrene A and polytrichastrol A with new skeletons, besides known wanju‐2,5‐diene and thunbergol. The enzyme mechanism was investigated by isotopic labeling experiments and DFT calculations to explain an unusual ethyl group formation. Rationally designed exchanges of active site residues showed major functional switches, resulting for I66F in the production of five more new compounds, including polytrichastrene B and polytrichastrol B, while A87T, A192V and the double exchange A87T, A192V gave a product shift towards wanju‐2,5‐diene.
Linalool synthase from Chryseobacterium polytrichastri was found to have diterpene synthase activity and produced diterpenes with new skeletons containing a rare ethyl group. Its formation was mechanistically studied through isotopic labeling and DFT calculations. Exchange of active site residues resulted in a functional switch leading to additional novel diterpenes. This work lays the ground for future rational engineering of terpene synthases.