Metabolism of Phospholipid 2-Linked Fatty Acids During the Release of Membrane Fragments from Haemophilus parainfluenzae by Ethylenediaminetetraacetic Acid-Tris(hydroxymethyl)-aminomethane

Membrane fragments containing diacyl phospholipids were released from viable cells of Haemophilus parainfluenzae during incubation in ethylenediaminetetraacetic acid (EDTA)- tris(hydroxymethyl)aminomethane (Tris) buffer. The phospholipids located in the part of the membrane that was released during the EDTA-Tris treatment had markedly different proportions of fatty acids than the lipids remaining in the cell residue. Very little metabolism of the 1-linked fatty acid occurred. After a short pulse with (14)C, the specific activity of the 1-linked fatty acid was lower in the phospholipids released than in the phospholipids of the residue, indicating an earlier time of synthesis of those lipids released in the membrane fragments. During the EDTA-Tris treatment, the 2-linked fatty acid was metabolized. This metabolism may have involved phospholipase A(2) which stimulates the synthesis of fatty acids and the transfer of acyl groups to the lysophospholipid.