Bioconversion of car-3-ene by a dioxygenase of Pleurotus sapidus

Mycelium of the basidiomycete Pleurotus sapidus known to contain a novel dioxygenase was used for the bioconversion of car-3-ene [I]. After 4 h of incubation 25.3 mg L−1 car-3-en-5-one [V], 5.4 mg L−1 car-3-en-2-one [VII], and 7.3 mg L−1 car-2-en-4-one [XV] accumulated as major oxidation products. The identity of the respective carenones and their corresponding alcohols was confirmed by comparison with MS and NMR spectral data obtained for synthesized authentic compounds. The peak areas of oxidation products were at least five times higher as compared with autoxidation. A radical mechanism similar to lipoxygenase catalysis was proposed and substantiated with detailed product analyses. The reduction of assumed car-3-ene hydroperoxides to the corresponding alcohols evidenced the radical initiated formation of hydroperoxides and confirmed the regio- and stereo-selectivity of the dioxygenase. The introduction of molecular oxygen into the bicyclic car-3-ene [I] molecule occurred at allylic positions of a cyclic isopentenyl moiety with a pronounced preference for the position adjacent to the non-substituted carbon atom of the C–C-double bond. This co-factor independent selective oxygenation presents an alternative to P450 mono-oxygenase based approaches for the production of terpene derived flavor compounds, pharmaceuticals and other fine chemicals.