A multifunctional lipoxygenase from Pyropia haitanensis- The cloned and functioned complex eukaryotic algae oxylipin pathway enzyme

Lipoxygenases (LOXs) are critical starting biocatalysts for the synthesis of signaling compounds derived from lipid peroxidation. However, LOXs from prokaryotes or lower eukaryotes always show nonspecific and multifunctional properties. Here, an oxylipin pathway enzyme gene of eukaryotic algae, Pyropia haitanensis of Bangiaceae (Rhodophyta), named PhLOX was cloned and characterized; a phylogenetic analysis was also performed. This unique LOX isoform is a multifunctional enzyme, combined unusually high hydroperoxidelyase (HPL), lipoxygenase, and allene oxide synthase (AOS) three catalytic activities within one catalytic domain of the protein, which may explain the observed diversity of P. haitanensis oxylipins. Phylogenetic analysis indicated that red algae LOXs separated from the LOX clades of the ancestor of higher plant and animal in the early stages of evolution. The substrate flexibility, oxygenation position flexibility, and functional versatility of PhLOX represented typical properties of lower organisms. These results indicated that the origin of the oxylipin biosynthetic gene and the oxylipin biosynthetic pathway of some red algae are unique, which may shed light on the specific defense strategies of these red algae and the evolution of the oxylipin pathway as well as the compact genome of red algae.