β-d-Galactosidase isoenzymes in different sheep organs

1. 1. Two types of β- d -galactosidase activity are present in sheep organs. 2. 2. A β- d -galactosidase that binds to concanavalin A and has an acidic pH-optimum, characteristic of a lysosomal hydrolase, predominates in sheep brain, kidney and spleen. 3. 3. A different β- d -galactosidase that does not bind to concanavalin A is also present in these tissues and accounts for 95% of the β- d -galactosidase in sheep liver. 4. 4. β- d -Glucosidase, β- d -fucosidase, β- d -xylosidase and α- l -arabinosidase activities also do not bind to concanavalin A. 5. 5. All five activities that do not bind to concanavalin A show the same pH-dependence, thermal stability and inhibition by Cl− ions and 2,5-dihydroxymethyl-3,4-dihydroxypyrrolidine (DMDP), a specific β- d -glucosidase inhibitor. 6. 6. It is postulated that a broad specificity glycosidase which has greatest activity towards β- d -glucosides accounts for all these activities. 7. 7. As the true β- d -galactosidase is not inhibited by DMDP it will be possible to use this inhibitor in a differential assay for the two types of β- d -galactosidase in sheep with a deficiency of the lysosomal β- d -galactosidase.