Δ6-Desaturase from Mortierella alpina: cDNA cloning, expression, and phylogenetic analysis.

The open reading frame of the Δ(6)-desaturase gene was isolated from Mortierella alpina W15 and the gene was cloned into a pPIC3.5K vector. The vector was transformed into Pichia pastoris GS115 and expression was induced with methanol. The Δ(6)-desaturase expressed in P. pastoris GS115 catalyzed the conversion of linoleic acid to γ-linolenic acid but not the conversion of α-linolenic acid to octadecatetraenoic acid. The results indicate that the Δ(6)-desaturase gene from M. alpina W15 has substrate specificity in different organisms. Phylogenetic analysis revealed that Δ(6)-desaturase genes can be divided into four monophyletic groups. This work paves the way for further study of the functions of Δ(6)-desaturase in fatty acid metabolism and its three-dimensional structure.