Specificity and Multiple Forms of P - Galactosidase in the Rat

1. Ten rat tissues and organs have been assayed for ,-galactosidase with phenyl ,B-D-galactoside, p-nitrophenyl B-D-galactoside, p-aminophenyl ,B-D-galactoside and 4-methylumbelliferyl fl-D-galactoside as substrates. 2. The relative activities of these tissues are independent ofthe mode ofassay, andmaximum rates ofhydrolysis are not greatly affected by the nature ofthe substrate. 3. Inhibition studies suggest the liver enzyme has no associated fl-glucosidase activity. 4. There is no cellular localization of preferential activity towards any of the four substrates in liver, kidney or spleen. 5. Evidence suggesting the non-destructive penetration of liver lysosomal membranes by p-nitrophenyl ,-D-galactoside is presented. 6. Liver lysosomal fl-galactosidase exists in multiple forms that can be separated on DEAEcellulose, and the enzyme components that are bound to the membrane appear to be similar to those of the lysosome sap. 7. The chromatographic pattern of enzyme excreted in the urine is compared with those from the kidney, intestine, spleen and liver.