Identification of novel mammalian phospholipids containing threonine, aspartate, and glutamate as the base moiety

In this study, we showed the occurrence of phosphatidyl-l-threonine (PThr), phosphatidyl-l-aspartate (PAsp), and phosphatidyl-l-glutamate (PGlu) in rat brain. Analyses using an HPLC–ESI-MS and an amino acid analyzer showed the presence of l-threonine, l-aspartate, and l-glutamate in the acid-hydrolysates of phospholipids from porcine cerebrum, rat cerebrum, and rat liver. Results of ESI-MS/MS analyses with neutral loss scanning and product ion scanning suggest the presence of PThr-(18:0, 18:1), PThr-(18:0, 22:6), PAsp-(18:0, 18:1), PAsp-(18:0, 22:6), PGlu-(18:0, 18:1), and PGlu-(18:0, 22:6) in rat brain. This is the first study to identify 2 novel phospholipids, PAsp and PGlu, with a carboxylate–phosphate anhydride bond, in living organisms.