Cell-free one-pot conversion of (+)-valencene to (+)-nootkatone by a unique dye-decolorizing peroxidase combined with a laccase from <italic>Funalia trogii</italic>.

A combined system of a unique dye-decolorizing peroxidase (Ftr-DyP) and a laccase obtained from the basidiomycete <italic>Funalia trogii</italic> converted the precursor (+)-valencene completely to the high-value grapefruit flavour constituent (+)-nootkatone, reaching a concentration maximum of 1100 mg/L. In the presence of 1 mM Mn2+ and 2.5 mM <italic>p</italic>-coumaric acid, (+)-nootkatone was the predominating volatile product, and only traces of substrate and the nootkatols were detectable after 24 h. Hence, the two-enzyme-system reproduced the oxidizing activity observed before for the crude culture supernatant. The newly discovered Ftr-DyP was purified, sequenced and further characterized as a thermostable, non-glycosylated protein with a pH-optimum in the acidic range and a calculated mass of 52.3 kDa. Besides the typical activity of DyPs towards anthraquinone dyes, Ftr-DyP also oxidized Mn2+ and showed activity in the absence of hydrogen peroxide. Neither the DyP from <italic>Mycetinis scorodonius</italic> nor the manganese peroxidase from <italic>Nematoloma frowardii</italic> were able to replace Ftr-DyP in this reaction. A hypothetical reaction mechanism is presented. [ABSTRACT FROM AUTHOR]