Abstract
1. 1. The stereospecific distribution of fatty acids in triacylglycerols was very similar in larvae and pharate adults of Ceratitis capitata. Palmitate accounted for about 70% of the fatty acids located at the sn-1 position whereas oleate was mainly restricted to the sn-2 position. 2. 2. The esterification of labelled 2-oleoyl- sn-[2 n- 3H]glycerol by mitochondrial and microsomal preparations from either larvae or pharate adults was higher than that of 2-palmitoyl- sn-glycerol. However, the capacity of both cellular preparations of the larvae for the acylation of the 2-acyl- sn-glycerols was higher than that of the pharate adult preparations. 3. 3. Double-label experiments using 2-oleoyl- sn-[2 n- 3H]glycerol and sn-[U- 14C]glycerol 3-phosphate were carried out to test the relative utilization of both substrates by cellular fractions of different stages of development of the insect. The monoacylglycerol pathway had a greater quantitative importance than the acylation of glycerol 3-phosphate by either mitochondrial or microsomal preparations. 4. 4. In vivo incorporation of 2-oleoyl- sn-[2 n- 3H]glycerol and [1- 14C]palmitate showed that both labelled precursors were maximally incorporated by the insect at the larval pupal apolysis stage. The labelling contributions of both moieties agreed with the important and different participation of the triacylglycerol acyltransferase activity in the mechanisms of lipid synthesis according to the stage of development. The fatty acid distribution of in vivo synthesized triacylglycerols showed a decrease of the de novo pathway of synthesis when development proceeds.
Published Version
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