The structure and biosynthesis of phosphatidyl inositol in cauliflower inflorescence.

Phosphatidyl inositol has been isolated from cauliflower inflorescence and soybean. Analysis of the fatty acid distribution showed that unsaturated fatty acids were preferred at position 2, and that saturated fatty acids were preferred at position 1.Mitochondrial preparations from cauliflower inflorescence were capable of synthesizing phosphatidyl inositol from myo-inositol and cytidine diphosphate diglyceride. The optimal pH for the reaction was 9.0. Metal ions were required for the reaction: Mn(2+) ions were optimally effective at 1.5 mm, and Mg(2+) ions were maximally effective at 30 mm. The maximal rate in the presence of Mn(2+) was 9 times as great as that in the presence of Mg(2+). Phosphatidyl inositol could also be synthesized when cytidine diphosphate diglyceride was replaced by cytidine triphosphate, but the pH optimum then shifted to 8.1.