The phospholipid acyl-chain dependence of the membrane-bound lysosomal beta-N-acetyl-D-glucosaminidase has been examined on control membranes from rat brain primary cell cultures and on membrane modified by culturing the cells in media supplemented with polyunsaturated fatty acids. The relationship between beta-N-acetyl-D-glucosaminidase activity and the membrane phospholipid acyl-chain composition has been evaluated. An increase in the unsaturation level of phosphatidyl ethanolamines and phosphatidylcholines, the most abundant phospholipids in this membrane fraction, is related to the rate of the enzymic reaction. The Arrhenius plot of the enzyme activity in modified membranes shows break-temperatures, starting from approximately 15 degrees C. The apparent activation energy below and above the break-temperature is not correlated with phospholipid acyl-chain unsaturation.
