title: Autoxidation versus biotransformation of alpha-pinene to flavors with Pleurotus sapidus: regioselective hydroperoxidation of alpha-pinene and stereoselective dehydrogenation of verbenol.
abstract: The enzymatic conversion of alpha-pinene to verbenols, verbenone, and minor volatile flavors was studied using submerged cultured cells, lyophilisate, and microsomal fractions of the edible basidiomycete Pleurotus sapidus . The similarity of the product range obtained by the bioconversions with the range of products found after autoxidation of alpha-pinene at 100 degrees C suggested similar initial pinene radicals. Extracts of the bioconversions were analyzed using thin layer chromatography with hydroperoxide staining and cool on-column capillary gas chromatography-mass spectrometry. Two isomer alpha-pinene hydroperoxides were identified as the key intermediates and their structures confirmed by comparison with synthesized reference samples and by microchemical reduction to (Z)- and (E)-verbenol. When the biocatalysts were supplemented with one of the verbenols, only the (Z)-isomer was oxidized, indicating the activity of a highly stereospecific monoterpenol dehydrogenase. The structural comparison of subunits shows that fungal oxifunctionalization reactions of some common terpene substrates, such as (+)-limonene or (+)-valencene, might likewise be catalyzed by dioxygenases rather than by CYP450 enzymes, as previously assumed.
authors.affiliation: Zentrum Angewandte Chemie der Leibniz Universitat Hannover, Institut fur Lebensmittelchemie, Callinstrasse 5, D-30167 Hannover, Germany. krings@lci.uni-hannover.de
authors.forename: Ulrich
authors.initials: U
authors.lastname: Krings
authors.forename: Nicole
authors.initials: N
authors.lastname: Lehnert
authors.forename: Marco A
authors.initials: MA
authors.lastname: Fraatz
authors.forename: Björn
authors.initials: B
authors.lastname: Hardebusch
authors.forename: Holger
authors.initials: H
authors.lastname: Zorn
authors.forename: Ralf G
authors.initials: RG
authors.lastname: Berger
mesh_terms: D000081008:Bicyclic Monoterpenes; D001711:Biotransformation; D005421:Flavoring Agents / Q000737:chemistry / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D039821:Monoterpenes / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D020076:Pleurotus / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D000081008:Bicyclic Monoterpenes; D005421:Flavoring Agents; D005656:Fungal Proteins; D039821:Monoterpenes; D010088:Oxidoreductases; C009951:verbenol; C005451:alpha-pinene