Reactions catalyzed by CYP74s.
CYP74A is an allene oxide synthase (AOS) and dehydrates 13-hydroperoxides of both linoleic and linolenic acids into unstable C18 allene oxides.
CYP74B2 catalyzes the cleavage of 13S-hydroperoxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid (linolenic acid 13-hydroperoxide) 10 times more efficiently than that of 13S-hydroperoxy-9(Z),11(E)-octadecadienoic acid (linoleic acid 13-hydroperoxide).