Effect of bile salts on lactosylceramide beta-galactosidase activities in human brain, liver and cultured skin fibroblasts.

The effect of bile salts on the hydrolysis of lactosylcermide by human beta-galactosidases in vitro was studied using cultured skin fibroblasts, liver and brain tissue. The evidence for two distinct enzymes that can catalyze the hydrolysis of lactosylceramide was observed when the bile salt was changed from pure sodium taurocholate to either crude taurocholate, or pure glycodeoxycholate, taurodeoxycholate or taurochenodeoxycholate. Tissues from patients with Krabbe's disease were found to be deficient in lactosylceramide beta-galactosidase activity (lactosylceramidase I) when pure taurocholate was used in the assay. When crude taurocholate was used in the assay, the Krabbe patients appeared to have normal activity for this enzyme. In place of crude taurocholate the pure salts of glycodeoxycholate, taurodeoxycholate and taurochenodeoxycholate worked even better to stimulate the second lactosylceramide beta-galactosidase activity and GM1 gangliosidosis patients exhibiting little if any activity. Therefore, lactosylcermidase I is stimulated by crude taurocholate or pure glycodeoxycholate, taurodeoxycholate and taurochenodeoxycholate. The use of pure bile salts to assay lactosylceramidase I and II will result in better reproducibility for these enzyme activities between laboratories.