Fatty Acid Distribution in Bacterial Phospholipids. The Specificity of the Cyclopropane Synthetase Reaction

The distribution of fatty acids in purified phospholipids isolated from several different bacteria has been examined by use of the specific phospholipase A of snake venom. In general the distribution is in accord with that found elsewhere in nature; the unsaturated acids are found in the β position and the saturated acids in the γ position. The distribution of cyclopropane fatty acids follows closely that of the unsaturated fatty acids. A notable exception was encountered with the phosphatidylethanolamine of Clostridium butyricum, in which unsaturated and cyclopropane fatty acids were found in more abundance in the γ position. The specificity of the C. butyricum cyclopropane synthetase reaction has been examined by employing as substrate a phosphatidylethanolamine with a known distribution of unsaturated fatty acids and analyzing the distribution of cyclopropane fatty acids in the phospholipid produced by the enzyme reaction. These experiments indicate that the enzyme has a definite, but not absolute, specificity for an unsaturated fatty acid in the γ position.