MOLECULAR SWITCH THAT CONTROLS THE FLUX OF LINOLEIC ACID INTO N-6 OR N-3 POLYUNSATURATED FATTY ACIDS IN MICROORGANISMS

Polyunsaturated Fatty Acids (PUFA) of the n-6 and n-3 series play important roles in nutrition. Microorganisms are important sources of n-6 and n-3 fatty acids; however, most produce either n-6 or n-3 fatty acids as the major PUFAs and very few produce both. This differential production suggests that PUFAs metabolic pathway is strictly controlled in microorganisms. The major pathway of n-6/n-3 faty acids biosynthesis in lower eukaryotes is composed of △12 Desaturase (Des), ω3 Des (△15, △17), △6 Des, △6 Elongase (Elo), △5 Des, △5 Elo and △4 Des, among which △6 Des and △15 (ω3) Des, located at the branch point of PUFAs metabolic pathways, are key regulators of the flux of linoleic acid (18:2 n-6) into either n-6 or n-3 fatty acid metabolic pathways. These latter two enzymes work together as a molecular switch that control the production of n-6/n-3 fatty acids. However the mechanism of the molecular switch is, so far, not clear. This review summarizes the recent advancement of the molecular base of the differentail production of n-6 or n-3 PUFAs in microorganisms.