Detection of divinyl ether synthase CYP74H2 biosynthesizing (11Z)-etheroleic and (1'Z)-colnelenic acids in asparagus (Asparagus officinalis L.)

Divinyl ether synthases (DESs) are the enzymes occurring in numerous plant species and catalysing the dehydration of fatty acid hydroperoxides to divinyl ether oxylipins, playing self-defensive and antipathogenic roles in plants. Previously, the DES activities and divinyl ethers were detected in some monocotyledonous plants, including the asparagus (Asparagus officinalis L.). The cloning of the open reading frame of the CYP74H2 gene of asparagus and catalytic properties of the recombinant CYP74H2 protein are described in the present work. The CYP74H2 utilized the 13(S)-hydroperoxide of linoleic acid (13(S)-HPOD) as a preferred substrate and specifically converted it to the divinyl ether, (9Z,11Z)-12-[(1'E)-hexenyloxy]-9,11-dodecadienoic acid, (11Z)-etheroleic acid. The second most efficient substrate after the 13(S)-HPOD was the 9(S)-hydroperoxide of alpha- linolenic acid (9(S)HPOT), which was converted to the previously undescribed product, (1'Z)-colnelenic acid. The 13(S)-hydroperoxide of alpha- linolenic acid (13(S)-HPOT) and 9(S)-hydroperoxide of linoleic acid (9(S)-HPOD) were less efficient substrates for CYP74H2. Both 13(S)-HPOT and 9(S)-HPOD were transformed to divinyl ethers, (11Z)etherolenic and (1'Z)-colneleic acids, respectively. The CYP74H2 is a second cloned monocotyledonous DES after the garlic CYP74H1 and the first DES biosynthesizing the (1'Z)-colneleic and (1'Z)-colnelenic acids.