A comparison of the properties and bile salt specificities of galactosylceramide and lactosyl ceramide beta-galactosidase activities in human leucocytes and fibroblasts.
The properties and bile salt specificities of galactosylceramide and lactosylceramide beta-galactosidase activities (GC and LC-beta-galactosidases) of human leucocytes and fibroblasts were compared. A number of differences were observed. Under the standard assay conditions the former activity was more sensitive to Zn2+ and Triton-X100. Glycocholate and cholate were more active stimulators of the GC-beta-galactosidase than the more frequently used taurocholate which was the most effective stimulator of LC-beta-galactosidase activity. It is postulated that some of the apparent differences in the properties of GC- and LC-beta-galactosidase activities may be attributed to the different micellar properties of the lipid substrates. Experiments with fibroblasts from patients with Krabbe's disease confirmed an almost total absence of GC-beta-galactosidase whichever bile acid was employed. Residual LC-beta-galactosidase activity detected in these cells was much higher ranging from 13% of the lowest measured value when measured with taurocholate to approximately normal values with glycocholate. Fibroblasts obtained from patients with GM1-gangliosidosis displayed close to normal GC and LC-beta-galactosidase activity under our experimental conditions. The data suggest that diagnoses of Krabbe's disease should be performed with galactosylceramide rather than lactosylceramide as substrate.
D001647:Bile Acids and Salts / Q000494:pharmacology*; D002412:Cations; D002554:Cerebrosides; D004789:Enzyme Activation; D005260:Female; D005347:Fibroblasts / Q000201:enzymology; D005696:Galactosidases / Q000378:metabolism*; D005699:Galactosylceramides; D006028:Glycosphingolipids; D006801:Humans; D007700:Kinetics; D007790:Lactosylceramides; D007962:Leukocytes / Q000201:enzymology*; D007965:Leukodystrophy, Globoid Cell / Q000201:enzymology; D008297:Male; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D015032:Zinc / Q000494:pharmacology; D001616:beta-Galactosidase / Q000378:metabolism*
D001647:Bile Acids and Salts; D002412:Cations; D002554:Cerebrosides; D005699:Galactosylceramides; D006028:Glycosphingolipids; D007790:Lactosylceramides; D005696:Galactosidases; D001616:beta-Galactosidase; D015032:Zinc