Monoacylglycerol pathway

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.

Moorhouse KG, Logan CJ, Hutson DH, Dodds PF (1990) The incorporation of 3-phenoxybenzoic acid and other xenobiotics acids into xenobiotic lipids by enzymes of the monoacylglycerol pathway in microsomes from adult and neonatal tissues. Biochem Pharmacol 39 1529-1536... 

Figure 4.10 Monoacylglycerol pathway for synthesis of triacylglycerol and formation of chylomicrons within the enterocyte.

Hansen, H.O., Jensen, S.S., Knudsen, J. 1986. Absence of monoacylglycerol pathway for triacylglycerol synthesis in goat mammary gland. Biochem. J. 238, 173-176. 

The monoacylglycerol pathway has also been demonstrated in the adipose tissue of the hamster and the rat. Under certain conditions it appears to compete with the glycerol phosphate pathway for acyl groups and may serve to regulate the activity of the latter pathway. The origin of the monoacylglycerol substrate in adipose tissue is not known. 

Anandamide amidase recognizes and hydrolyzes 2-AG (Goparaju, 1999 Di Marzo, 1999 Lang, 1999) however, there is evidence for the existence of another specific hydrolase [monoacylglycerol (MAG) lipase] that hydrolyzes 2-AG (D. Piomelli and A. Makriyannis, 2000, personal communication). In addition to this pathway, 2-AG diffuses rapidly into the cell membrane where it could be either hydrolyzed to arachidonic acid and glycerol or esterified back to phosphoglycerides (Di Marzo, 1999b). 

Fig. 2. Targeted lipidomics of 2-AG metabolism. Postulated pathways for 2-AG metabolism. Abbreviations PLC, phospholipase C DAG, diacylglycerol DGL, diacylglycerol lipase MGL, monoacylglycerol lipase PLA, phospholipase A AT, acyltransferase TAGL, triacylglycerol lipase PIP2, phosphatidylinositol bisphosphate ABHD-6/12 hydrolase lyso-PL, lysophospholipid lyso-PA, lysophosphatidic acid PA, phosphatidic add P, phosphatase COX, cydooxygen-ase LOX, lipoxygenase CYP450, cytochrome P450 CDP, cytidine diphosphate.

Thromboxane syn esis in platelets is triggered by the release of AA from platelet membrane phospholipids (14). This initial release appears to occur through activation of two major pathways a) the first pathway involves a sequoitial hydrolysis of 1, 2-diacylglycerol (DAG) fcxmed during platelet receptm -coupled activatirm of phospholipase C/D (PLC/PLD), by DAG- and monoacylglycerol (MAG) lipases, re )ectivefy (21,22). We have shown that hydrolysis of DAG by this pathwty results equimolar amounts of saturated fat acids (stearic palmitic acids) fixxn the sn-1 position and unsaturated fatty acids [oleic acid (18 1, -9), linoleic acid (18 2, co-6) and... 

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