Effects of fatty acid hydroperoxides produced by lipoxygenase in wheat cultivars during dough preparation on volatile compound formation

The formation of volatile compounds affects the flavor of processed wheat flour products. Herein, the effects of the composition of fatty acid hydroperoxides and the differences in the antioxidant contents among wheat cultivars on the flavor of wheat flour products were clarified. For this purpose, the volatile compounds in wheat flour doughs, LOX activity, fatty acid hydroperoxide composition from fractionated LOX, and antioxidant content were analyzed. Norin61 exhibited a high LOX activity and 9-fatty acid hydroperoxide production. Unsaturated aldehydes derived from 9-fatty acid hydroperoxides contributed significantly to the volatile compound profile of Norin61. Moreover, the lowest lutein content was observed in Norin61 among the analyzed cultivars. The LOX activity and composition of the fatty acid hydroperoxides produced by LOX affected the production of volatile compounds, whereas carotenoids had a suppressive effect. This study provides useful information for product design with the desired flavor for developing various processed wheat flour products.

The green microalga Lobosphaera incisa harbours an arachidonate 15S-lipoxygenase

The green microalga Lobosphaera incisa is an oleaginous eukaryotic alga that is rich in arachidonic acid (20:4). Being rich in this polyunsaturated fatty acid (PUFA), however, makes it sensitive to oxidation. In plants, lipoxygenases (LOXs) are the major enzymes that oxidise these molecules. Here, we describe, to our best knowledge, the first characterisation of a cDNA encoding a LOX (LiLOX) from a green alga. To obtain first insights into its function, we expressed it in E. coli, purified the recombinant enzyme and analysed its enzyme activity. The protein sequence suggests that LiLOX and plastidic LOXs from bryophytes and flowering plants may share a common ancestor. The fact that LiLOX oxidises all PUFAs tested with a consistent oxidation on the carbon n-6, suggests that PUFAs enter the substrate channel through their methyl group first (tail first). Additionally, LiLOX form the fatty acid hydroperoxide in strict S configuration. LiLOX may represent a good model to study plastid LOX, because it is stable after heterologous expression in E. coli and highly active in vitro. Moreover, as the first characterised LOX from green microalgae, it opens the possibility to study endogenous LOX pathways in these organisms.

WITHDRAWN: Structural and mechanistic studies of hydroperoxide conversions catalyzed by a CYP74 clan epoxy alcohol synthase from amphioxus (Branchiostoma floridae)

This manuscript has been withdrawn by the Author.