Phosphatidic acids, isolation structure

Lysophosphatidic acids, the structure of which is given in the next figure, have not yet been isolated from mammalian tissue. However, they are assumed to be intermediates in phosphatidic acid biosynthesis. 

Cardiolipin, a phospholipid originally isolated from heart muscle, has a similar structure. Inositol is replaced by glycerol which is esterified with phosphatidic acids in its a- and y-positions. 

A study has been made on the effects of PT and CTX on PLA2 hydrolytic activity of two PLA2 isolated from Crotalus molossus molossus venom (49). Unilamellar liposomes of various compositions were used in the study, which showed that PC liposomes were hydrolyzed faster in the absence of added PT or CTX. Addition of PT or CTX inhibited the activity on PC liposomes. The activities of the enzymes were profoundly enhanced on thionin-pretreated liposomes containing PS and on CTX-pretreated liposomes containing cardiolipin or phosphatidic acid. These data show that the two basic peptides modify phospholipid structure to affect the activity of added PLA2. 

The simplest type of phosphoinositide is represented by the phosphatide isolated from horse liver or dog liver by McKibbin.171 This consists only of glycerol, myo-inositol, phosphoric acid, and fatty acids it probably has structure LXXX. Similar inositides, differing only in the nature of the fatty acids, have been isolated from wheat germ,187 beef heart, 188 and beef liver.189 That the major portion of the fatty acids is attached to glycerol, not to myo-inositol, was shown by the isolation of a diglyceride on mild hydrolysis.189... 

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