Effect of bile salts on the hydrolysis of gangliosides, glycoproteins and neuraminyl-lactose by the neuraminidase of Clostridium perfringens

Studies were done on the effect of bile salts on the rates of hydrolysis of the N-acetylneuraminyl linkages of several sialic acid-containing compounds by the neuraminidase of C. perfringens. When G(M3)-ganglioside, two glycolipids (glycophorin and orosomucoid) and neuraminyl-lactose were used as substrates, hydrolysis was obtained even in the absence of bile salts, but addition of this detergent, below its critical micellar concentration, increased the reaction rates; above the critical micellar concentration of the detergent rates decreased again. When a second ganglioside, G(M1) was used as substrate, the requirement for bile salts was absolute; hydrolysis was not observed at all without this detergent. With increasing concentrations of bile salt and in the presence of high concentrations of enzyme, rates of hydrolysis increased, reaching maximal values at fixed ratios of bile salt to G(M1) ganglioside. Physical measurements showed that mixtures of bile salt and G(M1) ganglioside form mixed micelles that have a higher critical micellar concentration, a lower molecular weight and greater axial ratio than the corresponding micelles of pure G(M1) ganglioside.