ω3 fatty acid desaturases from microorganisms: structure, function, evolution, and biotechnological use

Abstract

The biosynthesis of very-long-chain polyunsaturated fatty acids involves an alternating process of fatty acid desaturation and elongation catalyzed by complex series of enzymes. ω3 desaturase plays an important role in converting ω6 fatty acids into ω3 fatty acids. Genes for this desaturase have been identified and characterized in a wide range of microorganisms, including cyanobacteria, yeasts, molds, and microalgae. Like all fatty acid desaturases, ω3 desaturase is structurally characterized by the presence of three highly conserved histidine-rich motifs; however, unlike some desaturases, it lacks a cytochrome b5-like domain. Understanding the structure, function, and evolution of ω3 desaturases, particularly their substrate specificities in the biosynthesis of very-long-chain polyunsaturated fatty acids, lays the foundation for potential production of various ω3 fatty acids in transgenic microorganisms.

Fig. 1

The major pathway of fatty acids biosynthesis in eukaryotic microorganisms. ΔN Des delta N fatty acid desaturase, ΔN Elo delta N fatty acid elongase, ω3 Des ω3 fatty acid desaturase

Fig. 2

Neighbor-joining tree showing the relationship among different ω3 desaturases and Δ12 desaturases. The Poisson model was used as the substitution model and gaps were treated using the method of pairwise deletion

Fig. 3

Topology model of ω3 desaturase from Mortierella alpina ATCC#32222. Cylinders A–F indicate membrane-spanning helices, and the black circles indicate three conserved histidine-rich motifs. Topology prediction was based on HMMTOP, TMPRED, and TMHMM algorithms