FATTY-ACID ELONGATION AND UNSATURATION BY MITOCHONDRIA AND MICROSOMES DURING DEVELOPMENT OF INSECTS

1. 1. In vitro desaturation and elongation activities of mitochondria and microsomes from the larval and pharate adult stages of development of the insect Ceratitis capitata have been studied with respect to cofactor requirements and two-carbon unit donor using radiogas chromatography. 2. 2. Larval mitochondria produced only the corresponding monounsaturated fatty acid and the more the length of the fatty acid carbon chain the more the desaturase activity of the preparation. Microsomes from larvae showed both desaturation and elongation activities. Desaturase activity required either NADH or NADPH as electron donor; elongation activity required malonyl-CoA whereas acetyl-CoA had no effect. 3. 3. Mitochondria and microsomes from the pharate adult stage of development were not able to desaturate fatty acids whereas elongation was slightly promoted by both cellular preparations. 4. 4. Patterns of in vivo modification of fatty acids were similar in both mitochondria and microsomes. However, it fails to obtain the desaturation products 12:1 and 14:1 from the 12:0 precursor, whereas elongation products have been found. 5. 5. Cytochrome b5 was shown in microsomes from larvae whereas it was not present in mitochondria from larvae and pharate adult particles. The activity of palmitate desaturase of mitochondria and microsomes from larvae was differently modulated by cyanide and carbon monoxide which suggests the existence of separate desaturating mechanisms. 6. 6. The extent of incorporation of the modified fatty acids into the lipid classes differed according to both the stage of development of the insect and the cellular fraction. © 1979.