The effects of detergents on CDP-choline:1,2-diacylglycerol phosphocholine transferase from hamster heart

The effects of detergents on CDP-choline:1,2-diacylglycerol phosphocholine transferase from hamster heart were examined. Maximum enhancement of enzyme activity was produced by Tween-20, while Triton X-100 caused a small increase in enzyme activity. No enhancement of enzyme activity was observed with deoxycholate or ethanol. Although enzyme activity was enhanced by different concentrations of Tween-20 (15-120 micrograms/mL), a substantially higher concentration of diacylglycerol was required when the concentration of Tween-20 in the assay was greater than 30 micrograms/mL. In the presence of Tween-20, a sigmoidal curve was obtained when enzyme activity was plotted versus diacylglycerol concentrations. The sigmoidal curve became more prominent when a higher amount of Tween-20 was used. It appears that the enhancement of enzyme activity by Tween-20 was not caused by the direct action of the detergent on the enzyme, but probably resulted in a better dispersion of the lipodal substrate which facilitates better utilization by the enzyme. The acyl specificity of the enzyme in the presence of detergent was found to be rather limited and the highest enzyme activity was obtained with diacylglycerols containing a monounsaturated acyl group at the C-2 position.