Identification and functional characterization of two Δ12-fatty acid desaturases associated with essential linoleic acid biosynthesis in Physcomitrella patens

Two Delta(12)-desaturases associated with the primary steps of long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis were successfully cloned from Physcomitrella patens and their functions identified. The open reading frames (ORFs) of PpFAD2-1 and PpFAD2-2 consisted of 1,128 bp and code for 375 amino acids. Their deduced polypeptides showed 62-64 % identity to microsomal Delta(12)-desaturases from other higher plants, and each contained the three histidine clusters typical of the catalytic domains of such enzymes. Yeast cells transformed with plasmid constructs containing PpFAD2-1 or PpFAD2-2 produced an appreciable amount of hexadecadienoic (16:2 Delta(9,12)) and linoleic acids (18:2 Delta(9,12)), not normally present in wild-type yeast cells, indicating that the genes encoded functional Delta(12)-desaturase enzymes. In addition, reduction of the growth temperature from 30 to 15 A degrees C resulted in increased accumulation of unsaturated fatty acid products.