Tissue fractionation studies. 4. Comparative study of the binding of acid phosphatase, β-glucuronidase and cathepsin by rat-liver particles

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Abstract
The [beta]-glucuronidase and cathepsin of rat liver share a number of the properties previously described for acid phosphatase. Like this enzyme, they are enclosed within cytoplasmic granules and exert their full activity in an in vitro assay only if the granules have been subjected to a treatment which simultaneously releases the enzymes in soluble form. The release of the 3 enzymes proceeds almost identically in washed particulate preparations activated either by the Waring Blendor, freezing and thawing, or exposure to hypotonic media. Incubation at 0[degree] in 0.15[image]-NaCl, or at 37[degree] and pH 5 in 0.25[image] sucrose also causes a parallel liberation of beta-glucuronidase and acid phosphatase. Cathepsin was not measured in these experiments. Once released, acid phosphatase and beta-glucur-onidase are easily separable by means of ammonium sulfate fractionation. The partial purification of acid phosphatase is described. It is concluded that the 3 enzymes behave essentially as though they were associated within the same granules. However, recent unpublished data suggest that this conclusion may have to be revised.