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Updated: Aug 14, 2026
In vivo Liver Endocytosis Followed by Purification of Liver Cells by Liver Perfusion
Published on: November 10, 2011
Effect of glycyl-L-phenylalanine 2-naphthylamide on invertase endocytosed by rat liver
Abstract:
The release by glycyl-L-phenylalanine 2-naphthylamide (Gly-L-Phe-2-NNap) of endocytosed invertase associated with the MLP fraction (sum of the M, L and P fractions [de Duve, Pressman, Gianetto, Wattiaux & Appelmans (1955) Biochem. J. 63, 604-617]) of rat liver was investigated and compared with the release of cathepsin C. The percentage of invertase released increases with time after the enzyme injection, whereas the release of cathepsin C is not influenced by this treatment and corresponds to 85-90% of the total activity of the enzyme. It takes about 2h to attain a similar release of both enzymes. The quantity of invertase releasable or not by Gly-L-Phe-2-NNap was plotted against the time after the injection. Results agree well with the hypothesis that unreleasable invertase is associated with a pre-lysosomal compartment, whereas releasable invertase is present in lysosomes. A kinetic analysis indicates that invertase enters the pre-lysosomal compartment with a zero-order rate constant of 0.48 unit/min per g fresh wt., and leaves this compartment with a first-order rate constant of 0.042 min-1.
Insights
Glycyl-L-phenylalanine 2-naphthylamide releases endocytosed invertase from rat liver lysosomes. Unreleasable invertase is in a pre-lysosomal compartment, while releasable invertase is in lysosomes.
Area of Science:
- Cell Biology
- Biochemistry
- Enzymology
Background:
- Endocytosis is a key cellular process for internalizing molecules.
- Lysosomes are crucial organelles for degradation within the cell.
- Enzyme localization within cellular compartments impacts their function.
Purpose of the Study:
- To investigate the release of endocytosed invertase from rat liver MLP fraction using Gly-L-Phe-2-NNap.
- To compare the release kinetics of invertase with cathepsin C.
- To determine the cellular localization of releasable and unreleasable invertase.
Main Methods:
- Enzyme activity assays for invertase and cathepsin C.
- Differential centrifugation to isolate rat liver MLP fraction.
- Kinetic analysis of enzyme release over time after Gly-L-Phe-2-NNap administration.
Main Results:
- Invertase release increased with time post-injection, unlike cathepsin C.
- 85-90% of cathepsin C activity was released, unaffected by the treatment.
- Kinetic data supported invertase residing in both pre-lysosomal and lysosomal compartments.
Conclusions:
- Gly-L-Phe-2-NNap effectively differentiates between lysosomal and pre-lysosomal invertase.
- Invertase entry into the pre-lysosomal compartment follows zero-order kinetics.
- Invertase exit from the pre-lysosomal compartment follows first-order kinetics.
