Oxidative desaturation of eicosa-8,11-dienoic acid to eicosa-5,8,11-trienoic acid: comparison of different diets on oxidative desaturation at the 5,6 and 6,7 positions

• Published in: Journal of lipid research Vol. 13; no. 6; pp. 783 - 789
• Main Authors: Castuma, J C, Catala, A, Brenner, R R
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01.11.1972
• Subjects: Animals; Carbon Isotopes; Chromatography, Thin Layer; Diabetes Mellitus, Experimental - metabolism; Diet; Dietary Fats - pharmacology; Dietary Proteins - pharmacology; essential fatty acid-deficient diet; fatty acid synthesis; Fatty Acids, Nonesterified - metabolism; Fatty Acids, Unsaturated - metabolism; linoleic acid; Linoleic Acids - metabolism; Male; microsomes; Microsomes, Liver - metabolism; oleic acid; Oleic Acids - metabolism; Oxidation-Reduction; Palmitic Acids - pharmacology; protein diet; Rats
• ISSN: 0022-2275; 1539-7262
• DOI: 10.1016/S0022-2275(20)39349-4

The oxidative desaturation of [1-(14)C]eicosa-8,11-dienoic acid to eicosa-5,8,11-trienoic acid by rat liver microsomes was studied, and the kinetic conditions appropriate to measure the specific activity of the enzyme were determined. A comparative study of the effects of a balanced diet and essential fatty acid-free diets on the oxidative desaturation of oleic and linoleic acids at the 6,7 position and the oxidative desaturation of eicosadienoic acid at the 5,6 position were made. Eicosadienoic acid showed a higher conversion than oleic acid for all the diets. The conversion of oleic and linoleic acids to Delta6 acids was equally increased by fat-free diets with or without added methyl palmitate, whereas the oxidative 5-desaturation of eicosadienoic acid at the 5,6 position was not changed. The effect was apparently independent of the amount of endogenous free fatty acids. The results suggest that the rate-limiting and principal regulatory step in the biosynthesis of eicosa-5,8,11-trienoic acid is the 6-desaturation of oleic acid. The 5-desaturation of eicosadienoic acid was increased by a protein diet and decreased by alloxan diabetes to a lesser extent than the 6-desaturation of linoleic acid. The 5-desaturation of eicosadienoic acid would constitute a secondary regulatory step.