Mechanism of thermal adaptation of membrane lipids in Tetrahymena pyriformis NT-1. Possible evidence for temperature-mediated induction of palmitoyl-CoA desaturase.

The regulatory mechanism of a key enzyme, palmitoyl-CoA desaturase, involved in the adaptation to temperature shift was investigated by labeling Tetrahymena pyriformis cells with [14C]palmitic acid. The rate of conversion of [14C]palmitate to [14C]palmitoleate was shown to be dependent on incubation temperature and also to be maximal at 2 h after the shift 39.5 to 15 degrees C. Addition of cycloheximide before the temperature shift produced no increase in desaturation of [14C]palmitate after the shift. These data would provide evidence for temperature-triggered increase of palmitoyl-CoA desaturase level and are also discussed in relation to membrane fluidity.