Fat metabolism in higher plants. XIV. Factors affecting the synthesis of oleic acid by particulate preparations from avocado mesocarp.

Numerous investigations have led to the point at which refined enzyme systems may be used to study the biosynthesis of saturated fatty acids (2, 3). The biosynthesis of unsaturated fatty acids has not been so thoroughly elucidated. Formation of unsaturated fatty acids has been observed experimentally in viva (4-9) and in vitro (10, 11) but several of these studies showed that incorporated radioactivity was distributed in the fatty acids in proportions quite different from the naturally occurring fatty acid composition. Whenever differences were found, the proportion of unsaturated fatty acids was low. Early experiments with slices, homogenates, and cell-free preparations from avocado mesocarp produced variable amounts of oleic and saturated fatty acid. It was, therefore, not feasible to compare the avocado system with that in a strain of Saccharomyces ceretisiae, which converted saturated fatty acids to unsaturated fatty acids by reactions requiring reduced triphosphopyridine nucleotide and oxygen (11). This report described conditions under which oleic acid is the principal acid formed from acetate by particulate preparations from avocado mesocarp. It is shown that oxygen is an absolute requirement for oleate biosynthesis in avocado.