Change of substrate specificity of rat liver microsomal fatty acyl-CoA synthetase activity by Triton X-100.

The effect of Triton X-100 on the activities and apparent molecular size of fatty acyl-CoA synthetase, solubilized and partially purified from rat liver microsomes, was studied. In the presence of Triton X-100, the activity for lignoceroyl-CoA synthesis was decreased, but activity was restored when the detergent was removed. The appearance and disappearance of lignoceroyl-CoA synthesis appeared related to the size of the aggregated form of the enzyme. On the other hand, activity for palmitoyl-CoA synthesis was not significantly affected by the detergent. Because available evidence suggests that both fatty acids are converted to CoA esters by the same enzyme, it seems likely that the substrate specificity of the enzyme is influenced by changes in the aggregation state and that the microenvironment of the enzyme in membranes may determine the substrate specificity of acyl-CoA synthetase.