Regulatory mechanism of palmitoyl-CoA desaturase activity in thermal adaptation. Induction in non-growing Tetrahymena cells deprived of pre-existing desaturase.

The regulatory mechanism of palmitoyl-CoA desaturase activity in the downward temperature shift was investigated in the non-growing (starved) Tetrahymena cells. This cell system is advantageous in allowing depletion of the pre-existing palmitoyl-CoA desaturase. An unexpectedly profound increase in its activity was observed following temperature shift from 34 degrees C to 15 degrees C, providing evidence to support the concept that the increased level of the desaturase activity results from induction of the desaturase synthesis, probably by reutilization of degraded cell components, rather than from direct membrane fluidity control as observed in different experiments.