Chapter 41 - Reaction Mechanism of the Strawberry Enone Oxidoreductase

Abstract

The flavor of strawberry (Fragaria×ananassa) fruit is dominated by an uncommon group of aroma compounds with a 2,5-dimethyl-3(5H)-furanone structure. Recently, we reported on the characterization of an enzyme involved in the biosynthesis of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF; Furaneol®), the key flavor compound in strawberries. Fragaria×ananassa enone oxidoreductase (FaEO), earlier putatively assigned as quinone oxidoreductase, catalyzes the formation of HDMF by the reduction of the α,β-unsaturated bond of the highly reactive precursor 4-hydroxy-5-methyl-2-methylene-3(2H)-furanone (HMMF). In vitro, the enzyme catalyzes the reduction of HMMF as well as 9,10-phenanthrenequinone (PQ; 2), although with differing mechanisms, via two-electron and one-electron reduction, respectively.