ISOLATION OF A DELTA(5)-FATTY ACID DESATURASE GENE FROM MORTIERELLA-ALPINA

Arachidonic acid (C20:4 Delta(5,8,11,14)) is a polyunsaturated fatty a cid synthesized by the Delta(6)-fatty acid desaturation of di-homo-gam ma-linolenic acid (C20:3 Delta(8,11,14)). I, mammals, it is known to b e a precursor of the prostaglandins and the leukotrienes but it is als o accumulated. by the filamentous fungus Mortierella alpina. We have i solated a cDNA encoding the Delta(5)-fatty acid desaturase from M. alp ina via a polymerase chain reaction-based strategy using primers desig ned to the conserved histidine box regions of microsomal desaturases, and confirmed its function by expression in the yeast Saccharomyces ce revisiae. Analysis of the lipids from the transformed yeast demonstrat ed the accumulation of arachidonic acid. The M. alpina Delta(5)-desatu rase is the first example of a cloned Delta(5)-desaturase, and differs from other fungal desaturases previously characterized by the presenc e of an N-terminal domain related to cytochrome b(5).