Formation of Monoenoic Fatty Acids by Desaturation in Rat Brain Homogenate

Desaturationof [1-r4C]stearic acid, [lJ4C]palmitic acid, and [l-14C]stearoyl-CoA was measured in homogenates of lo-day-old rat brain.Desaturation was maximal with stearoyl-CoA at pH 6.0 to 6.6.With free fatty acids, monoene formation was maximal at pH 7.2 to 7.6; stearic acid was more actively desaturated than palmitic acid.Activity with stearic acid or stearoyl-CoA was linear with protein concentration of 2 to 6 mg per ml and time to 10 min and was optimal at 37 to 45".At pH 7.4, fatty acid desaturation was not limited by the formation of fatty acyl-CoA derivatives when coenzyme A, Mg?+, and ATP were added.Rapid loss of activity in vitro prevented accurate subcellular location of the