Monoacylglycerol phosphate

Tjiong, H.B. Debuch H. Lysosomal bis (monoacylglycerol)phosphate of Rat Liver, Its Induction by Chloroquine and Its Structure. Hoppe-Seyler s Physil. Chem. 359, 71-79 (1978). 

BU4NF THE, AcOH, 62% yield. These conditions prevent the migration of acyl groups in bis(monoacylglycerol)phosphates. ... 

The lysosomal hydrolysis of SM to Cer and phosphocholine is catalyzed by acid SMase, a water-soluble, lysosomal glycoprotein that interacts with a sphingolipid-activator protein (SAP) and anionic lipids such as bis(monoacylglycerol)phosphate (BMP) to hydrolyze interfacial SM (T. Linke, 2001). Acid SMase possesses an N-terminal SAP-homology domain that appears to stabilize the correctly folded form of acid SMase as well as to facilitate the interfacial interaction with substrate in vivo (M. Kolzer, 2004). Acidic SMase is also secreted by many types of cells (I. Tabas, 1999 I. Takahashi, 2005). 

Figure 24-2. Biosynthesis of triaq/lglycerol and phospholipids. ( , Monoacylglycerol pathway (D, glycerol phosphate pathway.) Phosphatidylethanolamine may be formed from ethanolamine by a pathway similar to that shown for the formation of phosphatidylcholine from choline.

Monoacylglycerols, 10 802, 804, 822 Monoalkanolamine titanates, 25 95 Monoalkoxytriacyl titanates, 25 129 Monoalkylamines, 13 105 Monoalkylboranes, 13 632, 633, 635 Monoalkylhydrazines, 13 571 Monoalkyl phosphate extractants,... 

The incorporation of [ C]glycerol and [ CJglycerol phosphate into lipids was studied by Barron and Stumpf (1962). The active fraction obtained from avocado Persea americana L.) fruit mesocarp was purified by density gradient centrifugation, and most of the activity was found in the microsomal fraction. The first product was PA [but analysis at early time points detected lysophosphatidic acid (LPA)], followed by monoacylglycerol, diacylglycerol, and triacylglycerol in that order. 

LPA can be produced by several enzymatic routes (Figure 4). However, the relative contributions of these to LPA production is not known since specific inhibitors for many of the enzymes involved are not available (Pages et al., 2001). Firstly, de novo biosynthesis of LPA occurs by acylation of glycerol 3-phosphate, catalysed by glycerophosphate acyltransferase, in both the endoplasmic reticulum and mitochondria. Alternatively, LPA can be synthesized by the phosphorylation of monoacylglycerol or, in peroxisomes, by the reduction of acyl dihydroxyacetone phosphate. Subsequently, acylation of LPA by monoacylglycerolphosphate acyltransferase produces the precursor of all glycerophospholipids, phosphatidic acid. The latter can also act as a precursor of LPA synthesis by phospholipase A-catalysed deacylation. 

Finally, dephosphorylation of LPA to monoacylglycerol by lipid phosphate phosphatases can occur. 

The enzymes for phosphatidate synthesis, acyl CoA synthetase, glycerol 3-phosphate acyltransferase and monoacylglycerol acyltransferase, are on both the outer mitochondrial membrane and the endoplasmic reticulum membrane. Diacylglycerol acyltransferase is only on the endoplasmic reticulum it may use either diacylglycerol phosphate synthesized on the endoplasmic reticulum or that synthesized on the mitochondrion. Triacylglycerol synthesized on the endoplasmic reticulum membrane may then enter lipid droplets either in the cytosol or, in the liver and intestinal mucosa, the lumen of the endoplasmic reticulum for assembly into lipoproteins - chylomicrons in the intestinal mucosa (section 4.3.2.2) and very low-density lipoprotein in the liver (section 5.6.2). 

Monoacylglycerols and diacylglycerok can ako be esterified using phosphorus pentoxide. For example, esterification of 1,2-diacyl-sn-glycerol yields phosphatidic (1,2-diacyl-sn-glycerol 3-phosphate) and the corresponding bisphosphatidic acid and their positional isomers. Both acids are natural-identical products, which serve as substitutes for lecithin. Ammonium phosphatides (E442) are approved in the EU as emulsifiers. 

Frentzen, M., Heinz, E., McKeon, T.A., Stumpf, P.K. 1983 Specificities and selectivities of glycerol-3-phosphate acyl transferase and monoacylglycerol-3-phosphate acyl-transferase from pea and spinach chloroplasts. Eur. J. Biochem. 129, 629-636. 

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