Effect of Triton X-100 on the hydrolysis of sphingomyelin by sphingomyelinase of rat brain.

Mixed dispersions of the nonionic detergent Triton X-100 and sphingomyelin were used as substrate for sphingomyelinase of rat brain. The dependence of the rate of hydrolysis on the concentration of sphingomyelin was measured in two ways: at a fixed concentration of Triton X-100 or at varying concentrations of this detergent, while maintaining a fixed molar ratio of Triton X-100 to sphingomyelin. In either case, the upsilon vs. S curves deviated from the hyperbolic shape predicted by the Michaelis-Menten kinetic theory. These deviations are discussed and interpreted on the basis of the physicochemical properties of the mixed dispersions of detergent and lipid studied in previous papers.