Specificity and multiple forms of β-galactosidase in the rat

Abstract

1. Ten rat tissues and organs have been assayed for beta-galactosidase with phenyl beta-d-galactoside, p-nitrophenyl beta-d-galactoside, p-aminophenyl beta-d-galactoside and 4-methylumbelliferyl beta-d-galactoside as substrates. 2. The relative activities of these tissues are independent of the mode of assay, and maximum rates of hydrolysis are not greatly affected by the nature of the substrate. 3. Inhibition studies suggest the liver enzyme has no associated beta-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 beta-d-galactoside is presented. 6. Liver lysosomal beta-galactosidase exists in multiple forms that can be separated on DEAE-cellulose, 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.