Metabolism in the Crayfish Astacus Astacus (L.): IV. – The Fatty Acid Composition and the Biosynthesis of the Fatty Acids

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Abstract
The fatty acid composition of the crayfish Aslacus astacus (L.) was investigated. Fatty acid methyl esters were prepared and analysed by gas-liquid chromatography, Palmitic and oleic acid were the major components of the fatty acid mixtures. In addition to normal saturated and unsaturated fatty acids there were saturated and unsaturated odd-numbered fatty acids. Saturated branched-chain acids of the iso, anteiso and perhaps of the neo type have also been found. The biosynthesis of these fatty acids was studied by administration of sodium acetate-l-14C. The activity of most components of the fatty acid mixtures was determined by scintillation counting. It, was found that palmitic acid has a central place in the fatty acid metabolism. The non-mitochondrial system will be a very important system for storage of acetate units in the form of palmitic acid, while the mitochondrial or elongation system is also an important way of synthesis of fatty acids in Astacus. Possibly the mono-unsaturated fatty acids were derived from the saturated ones by dehydrogenation. The poly-unsa-turated acids of the C20 series must be synthesized from the essential linoleic acid by chain lengthening and successive dehydrogenations. On the basis of the results known from the literature, some possible pathways of synthesis of the odd-numbered and bran-ched-chain fatty acids were discussed.