Beta-xylosidase and beta-galactosidase activities of mammalian connective tissues and other sources

Cathepsin D. Characteristics of immunoinhibition and the confirmation of a role in cartilage breakdown

1. Antisera were raised against lysosomal cathepsin D of man, chicken and rabbit. 2. The antisera were found to be specific and potent inhibitors of cathepsin D activity. 3. The immunological nature of the inhibition was established. 4. The inhibitory effect was studied by varying pH, antiserum/enzyme ratio, time of incubation, concentration of components and order of mixing, and by using purified antibody and univalent antibody fragments. 5. The specificities of the antisera were examined with respect to other enzymes, isoenzymes of cathepsin D and cathepsin D from different organs. 6. The antisera prevented the action of cathepsin D on isolated proteoglycans and on cartilage. 7. The antisera produced up to 90% inhibition of the autolysis of cartilage from chicks and rabbits, indicating that cathepsin D is the enzyme mainly responsible for the breakdown of proteoglycans in this system.

Beta-D-glucosidases and related enzymic activities in pig kidney

1. The beta-glucosidase activity of pig kidney is located in the unsedimentable fraction of the cell and is not associated with the lysosomes. 2. The enzyme is active towards beta-d-glucosides, beta-d-galactosides, beta-d-xylosides and alpha-l-arabinosides. 3. These activities could not be separated by gel electrophoresis, gel filtration or DEAE-cellulose chromatography. 4. Response to inhibitors, heat-denaturation and competitive substrates suggests that a single active site is responsible for all four activities. 5. Two forms of the enzyme were found to occur either separately or together in kidneys of pigs from several different breeds. 6. Electro-focusing experiments show these to have a small difference in isoelectric point (4.9 and 5.1), and gel filtration gives an approximate molecular weight of 50000 for both forms. 7. The characteristics of these two enzymes are compared.