Stearoyl-CoA desaturase in mitochondrial membrane fractions

Several arguments suggested the possibility that the stearoyl-CoA desaturase might be located in the outer mitochondrial membrane in addition to its well presence in the microsomes. In the present investigation, preparations of rat liver microsomes and submitochondrial fractions (outer and inner membranes) were comparatively studied with respect to their stearoyl-CoA desaturase activities. Each fraction has been characterized by determinations of enzymic and chemical markers. This study revealed that while the activity of the stearoyl-CoA desaturase in microsomes was comparable to that found in other laboratories, a very low level of activity was detected in the mitochondrial outer membrane. The possible implications of the lack of stearoyl-CoA desaturase in mitochondria are discussed with respect to the lipid metabolism of these organelles.