Fatty acid desaturation by mammary gland microsomes from lactating mice

Abstract

Microsomal fractions obtained from lactating mouse mammary glands catalyze the desaturation of myristic, palmitic, and stearic acids in the presence of adenosine 5′-triphosphate, coenzyme A, and nicotinamide adenine dinucleotide, reduced form. The products of this reaction are the corresponding monoenoic fatty acids, myristoleic, palmitoleic, and oleic acids respectively. Desaturase, activity was greater with stearate as substrate than with either palmitate or myristate. Palmitate was desaturated at a rate ca. 50% greater than that of myristate. Although both nicotinamide adenine dinucleotide, reduced form and nicotinamide adenine dinucleotide phosphate, reduced form served as electron donors, the former was superior in this regard. Desaturase activity was not influenced by the addition of glycerol 3-phosphate to the incubation medium. However, the presence of this compound did affect the type of lipid formed. In the absence of the added glyceride-glycerol precursor, the major products were phospholipids, whereas in its presence they were triglycerides.