INVITRO OLEATE DESATURASE IN DEVELOPING SUNFLOWER SEEDS

The in vitro oleoyl phosphatidylcholine desaturase (ODS) activity in developing seeds of normal and high oleic sunflower lines has been studied. Lysophosphatidylcholine and sorbitol stimulated the enzyme activity, while Mg2+ was an absolute requirement. The microsomal fraction was the main site of ODS localization. The oil bodies fraction also retained some activity which could be removed after sonication. In the seeds of the normal genotype the microsomal ODS showed good activity throughout the period of active lipid synthesis. On the contrary, in the high oleic seeds this activity was lost at the beginning of this period. The microsomal ODS was strongly affected by incubation temperature and showed maximal activity at 20-degrees, suggesting that sunflower seeds could be a good model system to study temperature control of ODS enzyme activity.