Tissue fractionation studies. 9. Enzymic release of bound hydrolases

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Abstract
The percentage of free activity of 5 lysosomal enzymes (acid phosphatase, [beta]-glucuronidase, cathepsin, acid ribonuclease and acid deoxyribonuclease) has been measured on mitochondrial fractions from rat liver pre-incubated under mild conditions with various enzyme preparations. Clostridium welchii lecithinase, trypsin, chymotrypsin and pancreatin all caused a more or less important release of all enzymes which could be assayed. Ribonuclease and lysozyme, on the other hand, were without effect on the state of the acid hydrolases. In confirmation of previous data, these results have been taken to indicate that the release of the lysosomal enzymes is due to the disruption of a lipoprotein barrier restricting their physical freedom and their accessibility to their respective substrates. Further indications have been obtained that the internal cathepsin of the particles may be involved in the spontaneous disruption of the lyso-somes which occurs during incubation at pH 5.0 and 37[degree]. On the other hand, it has been found that this enzyme lags behind the others when their release is accomplished by the action of lecithinase.