The structure of phosphatidylglycerol (PG) 2 was es-Using chiral-phase high-performance liquid chromatablished by Benson and Mauro (1) who studied the tography (HPLC) and electrospray ionization-mass alga Scenedesmus. PG is now known to be widely disspectrometry (ESI/MS), we have redetermined the stetributed in animals, plants, and microorganisms (2), reochemical configuration of some natural and synthetic where it plays important roles as one of the acidic polyphosphatidylglycerols (PG). For this purpose, the synglycerophospholipids (3-5). The biosynthesis of PG in thetic and natural PG were converted to their bis-3,5mammalian tissues involves the reaction of CDP-DG dinitrophenylurethanes (DNPU), which were separated with sn-glycero-3-phosphate to form phosphatidylglycby HPLC using two columns having chiral phases of erophosphate which is subsequently dephosphorylated opposite configuration, (R)-(/)-and (S)-(0)-1-(1-naphto liberate the end product (2, 6). This biosynthetic thyl)ethylamine polymers. The molecular species were pathway is also shown to be active in plants and microidentified by on-line negative-ion ESI/MS. Absolute conorganisms (2). PG is also produced along with phosphafigurations of the resolved peaks were assigned by tidic acid from cardiolipin by the action of phospholicomparison with the elution order of the corresponding pase D (7). Both pathways are believed to yield 1(3)-monoacyl-sn-glycerol enantiomers as bis-DNPU deexclusively the 1,2-diacyl-sn-glycero-3-phospho-1-snrivatives on the same column. The results clearly glycerol (R,S configuration) (2, 7). On the other hand, showed that the PG from cabbage leaf lipids and soythe PG formed by transphosphatidylation from phosbean phospholipids consisted of single R,S isomers (1,2phatidylcholine and glycerol with phospholipase D has diacyl-sn-glycero-3-phospho-1-sn-glycerols), despite the been shown (8, 9) to be an equimolar mixture of the presence of nonstereospecific phospholipase D in the tisdiastereomeric 1,2-diacyl-sn-glycero-3-phospho-1-snsues. On the other hand, the PG derived from egg yolk
glycerol (R,S configuration) and 1,2-diacyl-sn-glycerophosphatidylcholine and glycerol by transphosphatidylation with cabbage phospholipase D was a mixture 3-phospho-3-sn-glycerol (R,R configuration) isomers, of 45% R,S isomers (1,2-diacyl-sn-glycero-3-phospho-1-although a circular dichroism study (10) has suggested sn-glycerols) and 55% R,R isomers (1,2-diacyl-sn-glycerothat this reaction also yields 100% naturally occurring 3-phospho-3-sn-glycerols). The PG from Escherichia coli R,S isomer. Since phospholipase D is widely distriblipids was a mixture of 89% R,S and 11% R,R isomers. uted in tissues, it could be a source of isomeric PG via The present study demonstrates that chiral-phase HPLC the transphosphatidylation reaction. Theoretically, up and negative-ion ESI/MS provide direct and unambiguto four stereoisomeric forms of PG could exist as the ous information about the configuration, identity, and molecule contains two chiral centers (Fig. ).
quantity of molecular species in natural and synthetic
Usually the PG structure is determined on the basis PG.