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

Abstract

The influence of various physical and chemical agents on the ability of cytoplasmic granules to retain acid phosphatase was investigated. The best protection of the complex was observed when the granules were kept at O[degree] in a medium containing 0.25 [image] sucrose or glycerophosphate. When these substances were absent or replaced by a variety of others, a progressive release of the enzyme occurred at a rate which was dependent on the nature of the substance added. The phenomenon was very rapid in distilled water, 0.25 [image] glycerol, and 0.15 or 0.44 [image].NaCl or KC1. It was completely inhibited when 0.25 [image] sucrose was present as well in the suspending medium. The rate of release in 0.25 [image] sucrose was increased by an increase in temp., and by addition of small amts. of saponin or desoxycholate. Acid phosphatase was easily adsorbed by various structural entities. In contrast to the native bound form of the enzyme, the adsorbed form was fully active enzymically, and was partly eluted by salts. From a consideration of all the exptl. data, it was concluded that the acid phosphatase-bearing granules are osmotic systems and must, therefore, possess a semipermeable membrane and an osmotically active internal medium.