Properties of cerebroside galactosidase

Abstract

Rat brain cerebrosidase was shown by centrifugal fractionation to be a lysosomal enzyme. The pH optimum was found to be 4.5. Taurocholate greatly stimulated its action. The addition of palmitic acid had little effect on the enzyme activity, but ceramide, sphingosine, and ceramide lactoside inhibited. Galactose, galactonolactone, and galactitol inhibited the enzyme, but the corresponding compounds with the glucose configuration did not. From this it may be concluded that the enzyme is active only toward galactosides, rather than glucosides. However, the enzyme preparation was able to hydrolyze ceramide glucoside, evidently because a second enzyme was present. The preparation was also active toward ceramide and ceramide lactoside, but rather inert toward galactosylgalactosylglucosyl ceramide. The molecular weight, determined by gel chromatography, was about 50000.The cerebrosidase occurring in the supernatant fluid of brain homogenates was shown by Sephadex chromatography to be associated with material of high molecular weight. The enzyme could be partially dissociated by addition of cholate plus Triton X-100. The crude cerebrosidase that was extractable from brain particles also showed associated and dissociated forms.