Bile salt activation of cerebroside sulphate sulphohydrolase.
The cholate and taurodeoxycholate activations of cerebroside sulphate sulphohydrolase (cerebroside-3-sulphate 3-sulphohydrolase, EC 3.1.6.8) activity of arylsulphatase A (aryl-sulphate sulphohydrolase, EC 3.1.6.1) were compared. Taurodeoxycholate caused a sharp peak of response at a concentration of 1.25 mg/ml (type-I activation). Cholate also showed type-I activation but, in addition, it evoked a second, higher, response plateau at concentrations between 5 and 10 mg/ml (type-II activation). At the pH of the reaction, cholate is converted largely to the sparingly soluble free aicd, so at the high concentrations associated with type-II activation, copious precipitates were formed. It was found that the precipitated material was essential for the type-II activation. Type-I activation appears to involve bile salt interaction with substrate, while type-II activation appears to involve enzyme interaction with solid-phase cholic acid. the putative mutant arylsulphatase A in an unusual form of metachromatic leukodystrophy hydolysed cerebroside sulphate only in the presence of high levels of cholate. The type-II activation may thus be simulating a physiological desulphation reaction.
D002553:Cerebroside-Sulfatase / Q000378:metabolism*; D002554:Cerebrosides / Q000378:metabolism; D011232:Chemical Precipitation; D002793:Cholic Acids / Q000494:pharmacology*; D003840:Deoxycholic Acid / Q000031:analogs & derivatives*; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D007966:Leukodystrophy, Metachromatic / Q000201:enzymology; D013429:Sulfatases / Q000378:metabolism*; D013657:Taurodeoxycholic Acid / Q000494:pharmacology*
D002554:Cerebrosides; D002793:Cholic Acids; D003840:Deoxycholic Acid; D013657:Taurodeoxycholic Acid; D013429:Sulfatases; D002553:Cerebroside-Sulfatase