Effect of lipids on activity and conformation of lysolecithin:lysolecithin acyltransferase from rabbit lung.

Lysolecithin:lysolecithin catalyzing two types of reaction, transacylation or hydrolysis, with the same substrate. Both activities have shown to be dependent on several environmental conditions and among them, the presence of lipids. The addition of several classes of lipids activated in all the cases the enzyme, decreasing the hydrolysis/transacylation molar ratio. This effect was higher for PC/PE/Chol mixture than for other lipids assayed. Circular dichroism spectra of the enzyme did not show any change with the addition of lipids, concluding that the effect of lipids was not due to any structural change in the protein. The hypothesis has been made of an influence of lipids on the physical state of the substrate as well as, possibly, on the enzyme-substrate interaction. The significance of these effects on the physiological role of lysolecithin-lysolecithin acyltransferase from soluble fraction of rabbit lung is discussed.