Isolation and characterization of Δ6-desaturase, an ELO-like enzyme and Δ5-desaturase from the liverwort Marchantia polymorpha and production of arachidonic and eicosapentaenoic acids in the methylotrophic yeast Pichia pastoris

The liverwort Marchantiapolymorpha contains high proportions of arachidonic and eicosapentaenoic acids. In general, these C20 polyunsaturated fatty acids (PUFA) are synthesized from linoleic and α-linolenic acids, respectively, by a series of reactions catalyzed by Δ6-desaturase, an ELO-like enzyme involved in Δ6 elongation and Δ5-desaturase. Here we report the isolation and characterization of the cDNAs, MpDES6, MpELO1 and MpDES5, coding for the respective enzymes from M.polymorpha. Co-expression of the MpDES6, MpELO1 and MpDES5 cDNAs resulted in the accumulation of arachidonic and eicosapentaenoic acids in the methylotrophic yeast Pichiapastoris. Interestingly, Δ6 desaturation by the expression of the MpDES6 cDNA appears to occur both in glycerolipids and the acyl-CoA pool, although other lower-plant Δ6-desaturases are known to have a strong preference for glycerolipids.