Glycerolipids phosphatidylcholine

FIGURE 25.19 Diacylglycerol and CDP-diacylglycerol are the principal precursors of glycerolipids in eukaryotes. Phosphatidylethanolamine and phosphatidylcholine are formed by reaction of diacylglycerol with CDP-ethanolamine or CDP-choline, respectively. 

Cool the tubes and add 75 (jlI of 1M KOH in methanol, sonicate and incubate for 2 hr at 37°C. This step removes most of the interfering glycerolipids, in particular phosphatidylcholines, that can mask sphingomyelins in a simple Mass spectrometry scan. 

Figure 21-3 Major pathways of synthesis of fatty acids and glycerolipids in the green plant Arabidopsis. The major site of fatty acid synthesis is chloroplasts. Most is exported to the cytosol as oleic acid (18 1). After conversion to its coenzyme A derivative it is converted to phosphatidic acid (PA), diacylglycerol (DAG), and the phospholipids phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE). Desaturation also occurs, and some linoleic and linolenic acids are returned to the chloroplasts. See text also. From Sommerville and Browse.106 See also Figs. 21-4 and 21-5. Other abbreviations monogalactosyldiacylglycerol (MGD), digalactosyldiacylglycerol (DGD), sulfolipid (SL), glycerol 3-phosphate (G3P), lysophosphatidic acid (LPA), acyl carrier protein (ACP), cytidine diphosphate-DAG (CDP-DAG).

Percoll gradient-centrifuged capacitated mouse sperm have in- 118. creased fertilizing ability and higher contents of sulfogalactosyl-glycerolipid and docosahexaenoic acid-containing phosphatidylcholine compared to washed capacitated mouse sperm. Biol. 119. Reprod. 2005 72 574-583. 

As noted above, chloroplasts and other plastids are enriched in galactolipids (Fig. 1). They also contain a unique sulfolipid, sulfoquinovosyldiacylglycerol, whose head group is a modified galactose. The phospholipid components of plastids are less abundant. Phosphatidylglycerol, the most prominent phospholipid contributor to the thylakoid membrane system, comprises less than 10% of chloroplast glycerolipids, while plastidial phosphatidylcholine is limited primarily to the organelle s outer membrane. 

Most glycerolipids are triacylglycerols, only about 4% are diacylglycerols or monoacylglycerols. Phospholipid (PL), phosphatidylcholine (PC), sphingomyelin (SM). 

Saturated fatty acids were initially incorporated only into the sn-1 positions of glycerolipids, principally phosphatidylcholine (PC) and triacyl glycerol (TAG). 

---