The multifunctional lipoxygenase PhLOX cloned from Pyropia haitanensis was expressed in Escherichia coli with 24.4 mg·L yield. PhLOX could catalyze the one-step bioconversion of C18-C22 fatty acids into C8-C9 volatile organic compounds (VOCs), displaying higher catalytic efficiency for eicosenoic and docosenoic acids than for octadecenoic acids. C20:5 was the most suitable substrate among the tested fatty acids. The C8-C9 VOCs were generated in good yields from fatty acids, e.g., 2E-nonenal from C20:4, and 2E,6Z-nonadienal from C20:5. Hydrolyzed oils were also tested as substrates. The reactions mainly generated 2E,4E-pentadienal, 2E-octenal, and 2E,4E-octadienal from hydrolyzed sunflower seed oil, corn oil, and fish oil, respectively. PhLOX showed good stability after storage at 4 °C for 2 weeks and broad tolerance to pH and temperature. These desirable properties of PhLOX make it a promising novel biocatalyst for the industrial production of volatile aroma compounds.

Background Algae respond to chemical and environmental stimuli in a way similar to higher plants. However, their receptors sensing stimuli remain a mystery. Results We identified and characterized one putative abscisic acid-G-protein coupled receptor homologous protein from red alga Pyropia haitanensis, Ph1205, and analyzed its evolution relationship, subcellular localization, and ligand-binding properties. Ph1205 contains 9 predicted transmembrane domains. Phylogenetic analysis revealed its early evolution. Recombinant expression of Ph1205-Egfp in HEK293T cells and immunofluorescence detection against N-terminal extracellular 14 amino acids (N14) of Ph1205 in Ph1205-transfected HEK293T cells and P. haitanensis protoplast confirmed its membrane location. Both N14 and Ph1205-transfected cells displayed high affinity with salicylic acid (SA) and oligoagar, which activated cAMP response element in HEK293T cells and upregulated luciferase activity. SA and oligoagar elicited similar but different transcriptional profiles of P. haitanensis, mainly by being involved in anabolic metabolism and cell growth. However, related intracellular signaling system in P. haitanensis has not yet fully evolved and evidently responded. Conclusions Our results demonstrate that Ph1205 displays some structural and functional characteristics as an early evolutionary membrane receptor, has potential extracellular-binding affinity to SA and oligoagar, and can activate heterotrimeric G-protein and CRE in animal cells.