Temperature and oxygen regulation of microsomal oleate desaturase (FAD2) from sunflower.

The effect of temperature and oxygen on the in vivo oleate desaturation and microsomal oleate desaturase (FAD2) activity was studied in peeled developing sunflower seeds. Using an oxygen concentration that was saturating for FAD2 enzyme, the amount of linoleic acid increased for all studied temperatures, being maximal at 20 degrees C. Under these conditions, FAD2 activity increased at the beginning of the incubation, remaining constant for the rest of the time, but reaching a lower level at 30 degrees C. Anoxia brought about a decrease in the FAD2 activity for all studied temperatures, becoming faster as the temperature increased. All these data suggest that temperature and oxygen control the level of FAD2 activity by separate mechanisms.