Tissue fractionation studies. 2. The nature of the linkage between acid phosphatase and mitochondria in rat-liver tissue

In the preceding paper (Berthet & Duve, 1951), the existence in rat-liver tissue of a mitochondrialinked form of acid phosphatase has been described and the cytological significance of this finding has been discussed.The nature of the linkage between enzyme and granule forms the object of the present communication.Two facts relevant to this problem have already been reported, namely the great lability of the complex, which can be disrupted quantitatively by mechanical or physical means (Waring blender, freezing and thawing, hypotonic media), and its lack of enzymic activity towards added glycerophosphate at pH 5. Considerations based on these and other properties to be described in this paper, indicate that the enzyme is retained inside the mito- chondrial structure by a membrane-like barrier, endowed with selective permeability and impermeable to glycerophosphate.A preliminary report of this work has already been published (Duve, Berthet, Berthet & Appelmans, 1951).