Hydrolysis of ceramide trihexoside by a specific -galactosidase from human liver

1. Partially purified ceramide trihexoside alpha-galactosidase from human liver was studied by using ceramide trihexoside specifically tritiated in the terminal galactose. 2. The hydrolysis of ceramide trihexoside was absolutely dependent on a mixture of sodium taurocholate and Triton X-100 and was markedly inhibited by human serum albumin and by NaCl. 3. The Lineweaver-Burk plot for ceramide trihexoside hydrolysis was upward curving. Ceramide lactoside inhibited hydrolysis of all concentrations of ceramide trihexoside. Ceramide digalactoside stimulated hydrolysis of low concentrations of ceramide trihexoside, but inhibited hydrolysis of high concentrations of the lipid. 4. alpha-Galactosidase activity assayed with the synthetic substrate 4-methylumbelliferyl alpha-d-galactopyranoside fractionated together with activity assayed with the natural substrate ceramide trihexoside. Both activities had identical heat-inactivation kinetics. 5. Characteristics of the hydrolysis of the synthetic substrate differed considerably from those of the natural substrate, including pH optimum, shape of the Lineweaver-Burk plot, and differential effects of inhibitors and activators. Mutual inhibition of hydrolysis between the synthetic and natural substrates was predominantly non-competitive. 6. These results are discussed in the light of special problems involved in the hydrolysis of lipids in an aqueous milieu.

The susceptibility of rat strains to experimental allergic encephalomyelitis

Nine rat strains were immunized with guinea-pig spinal cord emulsified with Freund's complete adjuvant. Five strains were relatively resistant to experimental allergic encephalomyelitis (EAE). In particular outbred Wistar rats did not produce more than a 25 per cent incidence of clinical disease although rats from four separate colonies were tried. Four strains were highly susceptible. An immunization schedule for producing a 95 per cent incidence of clinical and histological disease in one of these, inbred AS, is described. The importance of the dose of guinea-pig spinal cord in controlling the incidence of EAE and the production of antibodies to galactocerebroside was defined. The results do not support the previous suggestion that these antibodies might protect animals from EAE. There was no clear correlation, either positive or negative, between the titre of antibodies to galactocerebroside and the incidence of EAE in different strains.

Glucocerebrosidase: reconstitution of activity from macromolecular components

Glucocerebrosidase activity was reconstituted in vitro from a soluble glycoprotein factor (P) and a particle-bound factor (C). The physiological significance of the system is discussed.

Ceramidase deficiency in Farber's disease (lipogranulomatosis)

Ceramidase activity could not be demonstrated in the kidney and cerebellum from a deceased patient with Farber's disease, whereas the activities of six control acid hydrolase enzymes appeared normal. This enzyme defect presumably accounts for the accumulation that has been described in two patients and may represent the biochemical basis of this disorder.