POSITIONAL DISTRIBUTION OF OCTADECADIENOIC ACIDS IN SPONGE PHOSPHATIDYLETHANOLAMINES

The distribution of C14-C22 fatty acids in the phosphatidylethanolamin es isolated from the sponges Agelas sp. and Spongia tampa was investig ated. Selective changes with phospholipase A(2) (from Agkistrodon haly s blomhoffii) followed by thin-layer chromatographic separation of the resulting lysophosphatidylethanolamines and free fatty acids and subs equent methylation with HCl/MeOH and diazomethane, respectively, revea led that the 5,9 octadecadienoic acid and the 9,12-octadecadienoic aci d present showed no preference for either position sn-1 or sn-2 in the se phosphatidylethanolamines. The other saturated and unsaturated fatt y acids with chains between 14 and 22 carbons long were also found to be equally distributed between positions sn-1 and sn-2 in the phosphat idylethanolamines in these sponges. The results contrast with what is known about the distribution in most mammalian phospholipids, such as the phosphatidylcholines from human erythrocytes, where octadecadienoi c acid typically occupies the sn-2 position.