Analysis, distribution and function of unnatural glycerophospholipids in marine organisms

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The aim of this study was to clarify the distribution and physiological function of unusual glycerophospho- and glycolipids in marine organisms. For this purpose, chiral phase HPLC, reversed-phase HPLC and reversed-phase HPLC in conjunction with electrospray ionization mass spectrometry(ESI-MS) were applied to the separation and identification of stereoisomeric and regio-isomeric glycerolipids. Using these techniques, we found an unnatural phosphatidylglycerol (1,2-diacyl-sn-glycero-3-phospho-3'-sn-glycerol, R, R configurations at the two chiral centers) from various kinds of microorganisms including marine bacteria. The R, R isomer content increased with increasing culture temperature. The results strongly suggest that the bacteria adapt to temperature by alternating not only the degree of unsaturation but also the stereoisomer composition of phosphatidylglycerols. In the present study, we also investigated the separation and identification of the reverse isomers of glycerophospholipi … More ds (PtdCho,PtdEtn,PtdIno) and glycoglycerolipids (MGDG,DGDG,SQDG) by reversed-phase HPLC/ESI-MS. These glycerolipids were chromatographed as intact forms or 3,5-dinitrophenylurethanes of the 1,2-diacyl-sn-glycerols derived from the parent molecules. Excellent resolution was achieved for reverse isomers of very different pairs of acyl groups, such as 20:5-16:0 and 22:6-16:0, on highly efficient C18 columns. Using the method, we analyzed the glycerolipids from some fish and marine algae, and found that only MGDG from marine red algae, such as Porphyra yezoensis and Gracilaria verrucosa, gave two clearly resolved peaks, representing the reverse isomers of 20:5(sn-1)/16:0(sn-2) and 16:0(sn-1)/20:5(sn-2), and 20:4(sn-1)/16:0(sn-2) and 16:0(sn-1)/20:5(sn-2), respectively. The present method provides the first direct demonstration of the occurrence of reverse isomers in natural glycoglycerolipids and should be helpful in promoting work on the biosynthetic pathway and physiological importance of the reverse isomers in the red algae. Less