Abstract
Abstract The composition and metabolism of the fatty acids and lipids in the larval and adult forms of Spirometra mansonoides were studied. The parasite has a high content of cholesterol and of neutral and phospholipids which contain large amounts of polyunsaturated fatty acids. The fatty acid composition of the parasite closely resembles that of its host. S. mansonoides lacks the mechanisms required for the synthesis de novo of its sterols and long chain saturated and unsaturated fatty acids either in the presence or in the absence of molecular oxygen. By contrast, it possesses mechanisms for the synthesis of its own triglycerides, sterolesters, and phospholipids, with the use of exogenously supplied sterols and fatty acids.
Highlights
The major biosynthetic steps leading to the formation of sterols [1] and of saturated and unsaturated long chain fatty acids [2, 3] are known
The discovery that sterols and polyunsaturated fatty acids are not universal constituents of cells and that alternate pathways exist for the biosynthesis of unsaturated fatty acids has stimulated comparative biochemical studies [3]
These studies have resulted in several hypotheses which attempt to correlate the evolution of the different biosynthetic pathways of lipids with the functions of these compounds in different groups of organisms. One limitation of these studies is the fact that little information exists on the lipid metabolism of invertebrates other than the insects [4]
Summary
The composition and metabolism of the fatty acids and lipids in the larval and adult forms of Spiromefra mansonoides were studied. The lipid metabolism of parasitic helminths is of particular interest in that (a) these animals are relatively primitive invertebrates, and (b) the intestinal forms live in a predominantly anaerobic environment [5], they contain large amounts of cholesterol and polyunsaturated fatty acids [6], the biosynthesis of which requires molecular oxygen [2, 3] This somewhat puzzling situation might be explained by the possibility that oxygen is available in micro amounts, by the existence of a unique pathway of lipid biosynthesis, or by a dependence upon the host for these compounds. These findings have been reported in preliminary form [8]
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