Deacylation-reacylation reactions

Phosphatidylcholine can also be synthesized by the methylation pathway that converts phosphatidylethanolamine to phosphatidylcholine, principally in the liver. The methyl donor is S-adenosylmethionine (Chapter 17). Phosphatidylethanolamine-N-methyltransferase transfers three methyl groups in sequence to produce phosphatidylcholine. The fatty acid components of phosphatidylcholine can then be altered by deacylation-reacylation reactions. 

The fatty acid components of phospholipids made de novo are those of the precursors DGand CDP-DG. Once the phospholipid is made, the fatty acid substituents can be remodeled via deacylation-reacylation reactions (Fig. 10) [15]. Remodeling can occur at either the sn-l or sn-2 position of the glycerolipid. For example, a major molecular species of PC formed from the conversion of PE to PC is 16 0-22 6 (R.W. Samborski,... 

The 2 vitro data together with other vivo data (1) lead us to conclude that the deacylation and reacylation sequence must be an important means for establishing arachidonoyl-containing species of phosphatidyl inositol. There are, however, still some elements of the picture to be filled in. For example, there is minimal information about phospholipase A activity towards phosphatidyl inositol and, secondly, the presence of lysophosphatidyl inositol has yet to be demonstrated in fresh tissues which, of-course, is a requisite for the proposed deacylation - reacylation reactions. If lysophosphatidyl inositol does occur in tissues it must undoubtedly be present in very low concentrations. 

The labelling pattern of phosphatidyl inositol was quite different from that obtained by intraportal injections. There was an initial concentration of label in the monoenoic but with time this species became less labelled while the tetraenoic species progressively accumulated more label. This redistribution of counts we attribute to deacylation - reacylation reactions in which oligoenoic species, principally the monoenoic, are converted into tetraenoic by substitution of the fatty acids at position 2, and from the redistribution pattern this would appear to be very extensive. Thus, the pattern which takes hours to emerge with... 

The dealuminated Y(30) zeolite efficiently promotes the benzoyla-tion of 2-butylbenzofuran with para-anisoyl chloride or para-anisic acid the reaction is performed at 180°C in 1,2-dichlorobenzene (Table 4.6), and leads to the three acylated isomers 15,16, and 17 with a good initial selectivity in the 3-acylated derivative 15. The selectivity decreases with time due to the consecutive deacylation of this compound, followed by a reacylation that favors the formation of the other two isomers (mainly, the 6-acylated one). As expected, lower activity is observed when the carboxylic acid is utilized as acylating agent. 

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