Triacylglycerols biosynthesis

T Biosynthesis and degradation of triacylglycerols are regulated such that the favored path depends on the metabolic resources and requirements of the moment. The rate of triacylglycerol biosynthesis is profoundly altered by the action of several hormones. Insulin, for example, promotes the conversion of carbohydrate to triacylglycerols (Fig. 21-19). People with severe diabetes mellitus, due to failure of insulin secretion or action, not only are unable to use glucose properly but also fail to synthesize fatty acids from... 

The energy state of the cell dictates the relative rates of phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol biosynthesis. When energy is in short supply, the level of cAMP rises leading to inhibition of fatty acid biosynthesis (see chapter 18). This in turn decreases the supply of diacylglycerol, which limits the synthesis of phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol. When sufficient diacylglycerol is pres-... 

J Balsinde, EA Dennis. Bromoenol lactone inhibits magnesium-dependent phospha-tidate phosphohydrolase and blocks triacylglycerol biosynthesis in mouse P388D1 macrophages. J Biol Chem 271 31937-31941, 1996. 

Finally, genes required for particular aspects of fatty acid and triacylglycerol biosynthesis can be identified in appropriate sources, cloned, and transferred to other plants. Rapeseed has proved to be particularly flexible in this respect, and its fatty acid composition has been modified in several ways, some of which have now reached or are very close to commercial application (Section 9.4). Genetic modification procedures are also applied to soybean and other oilseed crops. 

The presence of partial glycerides in olive oil is due either to incomplete triacylglycerol biosynthesis or hydrolytic reactions. In virgin olive oil, the concentration... 

Key Words Acyltransferase Arabidopsis Brassica napus carbon flux fatty acid and triacylglycerol biosynthesis overexpression transcription factor. 

Shockey, J.M., S.K. Gidda, D.C. Chapital, et al. 2006. Tung tree DGATl and DGAT2 have nonredundant functions in triacylglycerol biosynthesis and are localized to different subdomains of the endoplasmic reticulum. Plant Cell 18 2294—2313. 

FIGURE 2.1 Schematic diagram of a-eleostearic acid and triacylglycerol biosynthesis in developing tung (Vernicia fordii) seeds. Eleostearic acid is synthesized from linoleic acid attached to endoplasmic reticulum (ER) phospholipids, primarily phosphatidylcholine (PC), then removed from the phospholipid pool and channeled into triacylglycerols through any of several coenzyme A (CoA)-dependent or -independent acyltransferase reactions. 

Bierhach, H. (1983) Triacylglycerol Biosynthesis in Human Small Intestinal Mucosal Acyl-CoA Monoglyceride Acyl-transferase, Digestion 28,138-147. 

Attree, S.M., Pomeroy, M.K, and Fowke, L.C. (1992) Manipnilation of conditions for the culture of somatic embryos of white spance for improved triacylglycerol biosynthesis and desiccation tolerance. Planta, 187 39S404... 

The oil bodies of C. abyssinica synthesized fatty acids from [ Cjmalonyl-CoA and triacylglycerols from [ C]palmitoyl-CoA or [ C]glycerol-3-P (Gurr et al., 1974). Evidence that this was not due to contamination was, first, that the fat fraction synthesized a pattern of fatty acids (predominantly erucic acid) totally different from that of other subcellular fractions and, second, that of all the fractions tested only the fat fraction had an appreciable specific activity for triacylglycerol biosynthesis. In ultrastructural studies, no inclusions could be seen in Crambe oil bodies, and it was concluded that the enzymes were contained in a bounding membrane or in granular material that was always associated with the oil body fraction (Fig. 12). 

Fig. 14. The kinetics of labeling of intermediates in triacylglycerol biosynthesis in avocado (P. americana) mesocarp. (Reproduced by permission of the Authors and Elsevier/North Holland Biomedical Press, B. V. from Barron and Stumpf, 1962.)...

Circumstantial evidence has accumulated for the role of phospholipids in providing diacylglycerols for triacylglycerol biosynthesis, but the details of the enzymology need to be confirmed. The extent to which and the manner in which diacylglycerol molecules are selected to enter the triacylglycerol pathway rather than for the synthesis of phospholipids is still unresolved. 

Bernerth, R., Frentzen, M. (1990) Utilisation of erucoyl-CoA by acyltransferases from developing seeds of Brassica napus (L.) involved in triacylglycerol biosynthesis. Plant Science 67,21-28. 

Lohden, I., Frentzen, M. (1992) Triacylglycerol biosynthesis in developing seeds of Tropaeolum majus L. and Limnanthes douglasii R. Br. Planta 188, 215-224. 

Hanke, C., Wolter, F.P., Coleman, J. Peterek, G., Frentzen, M. (1995) A plant acyltransferase involved in triacylglycerol biosynthesis complements an Escherichia coli 5 -l-acylgIycerol-3-phosphate acyltransferase mutant. Eur J Biochem 232, 806-810. 

Griffiths, G., Stymne, S. and Stobart, A.K. (1988b) The utilisation of fatty acid substrates in triacylglycerol biosynthesis by tissue-slices of developing safflower (Carthamus tinctorius L.) and sunflower (Helianthus annuus L.) cotyledons. Planta 173, 309-319. 

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