Enzyme deletions and essential fatty acid metabolism in cultured cells

Conversion of 14C-labeled linoleic acid to dihomo-gamma-linolenic and arachidonic acids, precursors of the PG1 and PG2 series of prostaglandins, was examined in a number of mammalian cell lines in tissue culture. Diploid cells converted linoleate to arachidonate in good yield. Heteroploid or transformed cells did not desaturate linoleic acid but readily converted dihomo-gamma-[14C]linolenate to arachidonate. These observations demonstrate that separate delta6 and delta5 desaturases are involved in the conversion of linoleic to arachidonic acid in mammals. The results indicate that loss or modification of the delta6 desaturase system is a frequent occurrence in transformed cells.