Enzymatic study of GM-1 gangliosidosis.

Two types of GM-1 gangliosidosis were studied biochemically. Type 1 liver accumulated non-lipid hexosamine in addition to GM-1 ganglioside, but there was no increase of hexosamine and GM-1 in type 2 liver. The optimum pH of liver beta-galactosidase of type 1 and type 2 was 5--6 while that of the normal control was 4.5. Type 1 brain beta-galactosidase showed a slightly acidic optimum pH, i.e. 4.0 in comparison with that of the normal control. The optimum pH of type 2 brain beta-galactosidase was 5.5, like the liver enzyme. The thermostability of liver beta-galactosidase was the same in type 1 and type 2, while that of brain was different. Beta-galactosidase of type 1 and type 2 liver is more stable at 42 degrees C than the normal control, but a different thermostability was observed in type 1 and type 2 brain. Liver beta-galactosidase of type 1 showed one peak each at acid and neutral pH, and type 2 liver had only one peak at neutral pH.