ABSTRACT
Cholinephosphotransferase, the enzyme responsible for the terminal reaction in the formation of phosphatidylcholine (PC) in lung, has been extensively examined in lung. Pulmonary surfactant stabilizes the lung by reducing the surface tension at the air-liquid interface of the alveolar surface. The deacylation-reacylation, or “Land’s cycle”, can account for many of the observations made with fractions from whole lung or type II cells. The crucial role of cholinephosphate cytidylyltransferase in the increase in PC production is further suggested by studies with fetal rat lung. The disaturated PC in lung can be synthesized partly via the de novo pathway, but also through a progressive conversion of unsaturated PCs generated by the de novo pathway into their disaturated counterparts. The lack of correlation between the increase in the incorporation of choline into PC and the activities of the enzymes involved in PC production prompted examination of the pool sizes of choline and its intermediates in rabbit lung.
