A Requirement for Lipids by the Microsomal Stearyl Coenzyme A Desaturase

Abstract

Abstract Hen liver microsomes, when extracted with aqueous acetone, lose their ability to desaturate stearyl coenzyme A to oleate. The desaturase activity of these particles is partially restored by addition of lipid micelles prepared from microsomal lipid. Fractionation of the microsomal lipid yields fractions which are tested for their ability to restore the desaturase activity. A mixture of phospholipids, triglycerides, and fatty acids is able to restore the desaturase activity of the acetone-extracted microsomes to the level of the original microsomes. Phosphatidylcholine, isolated from the phospholipid, can partially replace phospholipids in this mixture. The properties of the reconstituted system are similar to those of the original microsomes. There is an absolute requirement for oxygen and a reduced pyridine nucleotide, although DPNH, rather than TPNH, is the preferred electron donor. The similarities between the lipid requirements of the DPNH-cytochrome c reductase and the stearyl-CoA desaturase support the suggestion that the two systems share a common electron transfer pathway or carrier.