Biosynthesis of Dipalmitoyllecithin by the Rabbit Lung

Publisher Website
Google Scholar
Abstract
The esterification of palmitate by lung homogenates is increased by palmitoyllysolecithin in the presence of CoA and ATP. [32P]lysolecithin can also be converted to [32P]lecithin in the absence of other substrates, suggesting transacylation between two molecules of palmitoyllysolecithin. Some palmitate is esterified in the absence of added lysolecithin, ATP, and CoA. Free palmitate appears to exchange with other esterified fatty acids, especially oleate incorporated into the lecithin of lung tissue slices. The lung contains sufficient 1-palmitoyl-2-oleyllecithin for this exchange to be significant. In homogenates, Ca2+ is required for the exchange and the incorporation of palmitate. The in vivo turnover of the oleate in the lecithin of lung tissues and bronchiolar washings is more rapid than that of the palmitate. This is consistent with a mechanism of dipalmitoyllecithin synthesis involving exchange of esterified oleate for palmitate in lecithin. It is concluded that in addition to de novo synthesis of lecithin in the lung, incorporation of activated palmitate into lysolecithin and exchange of palmitate with oleate esterified in endogenous lecithin also occur. Phospholipase activity is probably involved in the latter two pathways.

This publication has 0 references indexed in Scilit: