The biosynthesis of triacylglycerols

1 Pathways for complete (de nove) synthesis these pathways build up the molecules from small basic constituents 

PATHWAY phosphate acetone phosphate PHOSPHATE PATHWAY 

Kennedy also demonstrated the central role of phosphatidic acid in both phospholipid (section 7.1.2) and triacylglycerol biosynthesis and one of his outstanding contributions has been to point out that the diacylglycerol derived from phosphatidic acid forms the basic building block for triacyl-glycerols as well as phosphoglycerides. 

After non-esterified fatty acids are attached to CoA in the plastid envelope they can, apparently, move rapidly to the endoplasmic reticulum. It is not known how this transport takes place, although lipid-binding 

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. 

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Section 26 4 Phospholipids are intermediates in the biosynthesis of triacylglycerols from fatty acids and are the principal constituents of the lipid bilayer component of cell membranes... 

Phosphatidic acids not only are intennediates in the biosynthesis of triacylglycerols but also are biosynthetic precursors of other members of a group of compounds called phosphoglycerides or glycerol phosphatides. Phosphorus-containing derivatives of lipids are known as phospholipids, and phosphoglycerides are one type of phospholipid. 

Diacylglycerol is glycerol esterified to two fatty acids at the sn-1 and sn-2 positions. It is a membrane-embedded product of phospholipase C action and an activator of protein kinase C. It is also an intermediate in the biosynthesis of triacylglycerol, phosphatidyletha-nolamine and phosphatidylcholine. 

Phosphatidate Is the Common Precursor in the Biosynthesis of Triacylglycerols, Many Phosphoglycerols, Cardiolipin... 

Tijburg LBM, Geelen MJH, van Golde LMG Regulation of the biosynthesis of triacylglycerol, phosphatidylcholine and phos-phatidylethanolamine in the liver. Biochim Biophys Acta 1989 1004 1. 

Figure 21-5 A more complete outline of the biosynthesis of triacylglycerols, glycolipids, and phospholipids including characteristic eukaryotic pathways. Green lines indicate pathways utilized by both bacteria and eukaryotes. Structures of some of the compounds are shown in Fig. 21-4. The gray arrows show the formation of phosphatidylserine by exchange with ethano-lamine (Eq. 21-10).

Phosphatidic acid A compound of the type shown, which is an intermediate in the biosynthesis of triacylglycerols. 

Stymne, S. and Stobart, A.K. 1984b. The biosynthesis of triacylglycerols in microsomal preparations of developing cotyledons of sunflower (Helianthus annuus L.). Biochem. J. 220 481-188. 

In plants, triacylglycerols are mainly synthesized and stored in the cotyledons of the seed (e.g. sunflower, soya, rape), the mesocarp of the fruit (avocado, oil palm) or the endosperm tissue (castor bean, coconut). Although the main pathways for the biosynthesis of triacylglycerols in plants have now been elucidated, the control of lipid biosynthesis in plants is little understood. 

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