Phosphatidyl-glycerol-3-phosphate

Fig. 6. Synthesis of phospholipid polar head groups. The three major phospholipid species in E. coli are synthesized by a total of six different enzymatic activities (1) phosphatidate cytidylyltransferase (Cds), (2) phosphatidylserine synthase (PssA), (3) phosphatidylserine decarboxylase (Psd), (4) phosphatidyl-glycerol phosphate synthase (PgsA), (5) phosphatidylglycerol phosphate phosphatase (PgpA or PgpB), and (6) cardiolipin synthase (els).

Figure 16.1 Networks of the major pathways for biosynthesis of glycerophospholipids in different species as indicated. SAM and PGP denote S-adenosylmethionine and phosphatidyl-glycerol phosphate, respectively. All other abbreviations can be found in the list of abbreviations. (a) Animals and plants (b) yeast and (c) bacteria.

The other phospholipids can be derived from phosphatidates (residue = phosphatidyl). Their phosphate residues are esterified with the hydroxyl group of an amino alcohol choline, ethanolamine, or serine) or with the cyclohexane derivative myo-inositol. Phosphatidylcholine is shown here as an example of this type of compound. When two phosphatidyl residues are linked with one glycerol, the result is cardiolipin (not shown), a phospholipid that is characteristic of the inner mitochondrial membrane. Lysophospholipids arise from phospholipids by enzymatic cleavage of an acyl residue. The hemolytic effect of bee and snake venoms is due in part to this reaction. 

This enzyme [EC 2.7.8.5] (also referred to as phosphati-dylglycerophosphate synthase, glycerophosphate phos-phatidyltransferase, and 3-phosphatidyl-l -glycerol-3 -phosphate synthase) catalyzes the reaction of CDP-diac-ylglycerol with glycerol 3-phosphate to produce CMP and 3-(3-phosphatidyl)glycerol 1-phosphate. 

Glycerol is phosphorylated to glycerol-3-phosphate (G-3-P) by glycerol kinase (ATP glycerol-3-phosphotransferase, EC 2.7.1.30) [5]. G-3-P is also known as sn-glycerol 3-phosphate, glycerophosphoric acid, phosphatidyl glycerol, and sn-Gro-... 

Studies with mutant strains of E. coli have demonstrated that there is a connection between the turnover of membrane phospholipids and the synthesis of the so-called membrane-derived oligosaccharides , which are D-gluco-oligo-saccharides variously substituted with sn-glycerol phosphate, ethanolamine phosphate, and succinate on the outer envelope of the cell. The glycerol phosphate residues of these oligosaccharides appear to be donated by phosphatidyl-glycerol or the lipid cardiolipin or both. 

Abbreviations DAG, diacylglycerol LPA, lyso phosphatidic acid LPIP, lyso phosphatidyl inositol 4-phosphate PA, phosphatidic acid PC, phosphatidyl choline PE, phosphatidyl ethanolamine PG, phosphatidyl glycerol PI, phosphatidyl inositol PIP, phosphatidyl inositol 4-phosphate PIP2 phosphatidyl inositol 4,5-bisphosphate ... 

Phosphatidyl choline (lecithin), phosphatidyl serine, phosphatidyl glycerol, phosphatidyl inositol, phosphatidic acid, sphingomyelin. OCDG, dihexadecyl phosphate, dialkyl dimethyl ammonium salts... 

Phospholipids containing phosphatidyl, inositol, lecithin, serine, and ethanolamine (Stevenson 1986) are the second most abundant identifiable form of organic P in the upper layer of the subsurface. These groups contain glycerol, fatty acids, and phosphate (Sims and Pierzjinski 2005). The P in the structure is a diester, which is more susceptible to degradation in soils than monoesters. 

Bacteria and plants often make the anionic phosphatidyglycerol in which the second glycerol is esterified at its sn-1 position with the phosphate. Bacteria, as well as mitochondria, contain diphosphatidylglycerol (cardiolipin) in which phosphatidyl groups are attached at both the 1 and 3 positions of glycerol (Fig. 8-2). 

---