Disclosed are isolated polynucleotides encoding an omega-3 desaturase and adelta-12 desaturase, the enzymes encoded by the isolated polynucleotides,vectors containing the isolated polynucleotides, transgenic hosts that containthe isolated polynucleotides that express the enzymes encoded thereby, methodsfor producing the desaturase enzymes, and method of using the enzymes to makepolyunsaturated fatty acids. The isolated polynucleotides are derived from afungus, Saprolegnia diclina (ATCC 56851). In particular, omega-3-desaturasemay be utilized, for example, in the conversion of arachidonic acid (AA) toeicosapentaenoic acid (EPA). Delta-12 desaturase may be used, for example, inthe conversion of oleic acid (OA) to linoleic (LA). EPA or polyunsaturatedfatty acids produced therefrom may be added to pharmaceutical compositions,nutritional compositions, animal feeds, as well as other products such ascosmetics.
