Triacylglycerol monoacylglycerol pathway

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. 

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.

The synthesis by route C is an alcoholysis reaction. The reaction proceeds as an emulsion due to the immiscibility of triacylglycerol and glycerol. Under this emulsified condition, the equilibrium concentration of the monoacylglycerol is 30% (Yamane et al., 1986). However, when the reaction is run at temperatures slightly below the melting point of the fat used, the concentration is favourably increased to 70-90% (McNeill et al., 1990 McNeill and Yamane, 1991). The reaction rate is affected by moisture content. Relatively high moisture leads to high initial reaction rates (McNeill et al., 1991) but excessive levels result in hydrolysis and production of free fatty acids. Compared to the synthetic pathways of A and B, route C seems a cheaper alternative since the primary reactive components do not include free fatty acids reactants that otherwise would have to be produced by other methods to make them available for the process. 

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