The present invention relates to a polynucleotide encoding an omega 3 (ω-3)desaturase from Pythium irregulare with specificity to long chain polyunsaturatedomega 6 (ω- 6) fatty acids as well as a vector containing said polynucleotide,and a host cell containing the vector or the polynucleotide. Moreover, the presentinvention pertains to a polypeptide encoded by the said polynucleotide, antibodiesagainst the polypeptide as well as a method for the manufacture of the polypeptide.Further, encompassed by the present invention are transgenic non-human organisms.Finally, the present invention relates to methods for the manufacture of compoundsand oil- fatty acid- or lipid- containing compositions.
