Acyl carrier protein derivatives desaturation

Acyl carrier protein, fatty acid synthase sequence, 45-46 Acyl carrier protein derivatives, desaturation, 13,l4f Acyl lipids, formation, 47-48 Aglycone skeletons saponins, 288f Solanum glycoalkaloids, 288f... 

Figure 21-3 Major pathways of synthesis of fatty acids and glycerolipids in the green plant Arabidopsis. The major site of fatty acid synthesis is chloroplasts. Most is exported to the cytosol as oleic acid (18 1). After conversion to its coenzyme A derivative it is converted to phosphatidic acid (PA), diacylglycerol (DAG), and the phospholipids phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE). Desaturation also occurs, and some linoleic and linolenic acids are returned to the chloroplasts. See text also. From Sommerville and Browse.106 See also Figs. 21-4 and 21-5. Other abbreviations monogalactosyldiacylglycerol (MGD), digalactosyldiacylglycerol (DGD), sulfolipid (SL), glycerol 3-phosphate (G3P), lysophosphatidic acid (LPA), acyl carrier protein (ACP), cytidine diphosphate-DAG (CDP-DAG).

It is as yet unknown whether the substrates of the enzymes involved in the synthesis of dihydrosterculic acid are specific phospholipids, acyl-CoA, acyl-acyl carrier protein (ACP) or even free fatty acids. The preferred substrates of bacterial cyclopropanoid fatty acid synthesis are phosphatidyl-ethanolamines (Christie, 1970 O Leary, 1965 Hofmann, 1%3 Law, 1971). The true substrate of the desaturating enzyme is also yet to be identified. It is well known that exogenous stearic acid, a straight-chain saturated fatty acid, is not desaturated to oleic acid unless it is supplied as the ACP derivative (Shine et al., 1976). In contrast, dihydrosterculic acid, a cyclic saturated fatty acid, is desaturated to stercuiic acid when supplied as such. 

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