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Proteolytic activation of human procathepsin D
1Department of Cell Biology and Anatomy, University of Miami School of Medicine, Florida.
Advances in Experimental Medicine and Biology
|January 1, 1991
Summary
Procathepsin D can partially activate itself into pseudocathepsin D. However, full conversion to active cathepsin D requires a second enzyme, suggesting a unique activation pathway for this aspartyl protease.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Cathepsin D is a crucial lysosomal aspartyl protease.
- Procathepsin D is its short-lived, inactive precursor.
- Understanding procathepsin D activation is key to lysosomal enzyme function.
Purpose of the Study:
- To investigate the activation pathway of procathepsin D.
- To identify the mechanisms and intermediates involved in cathepsin D maturation.
- To compare procathepsin D activation to other aspartyl proteases.
Main Methods:
- Pulse-chase analysis with radiolabeled amino acids.
- In vitro autocatalytic cleavage assays using purified procathepsin D.
- Expression of non-glycosylated procathepsin D in bacterial systems.
- Inhibition studies using protease inhibitors like leupeptin.
Main Results:
- Demonstrated autocatalytic cleavage of procathepsin D to pseudocathepsin D.
- Identified biosynthetic intermediates during cathepsin D formation.
- Showed that complete conversion to single-chain cathepsin D requires a leupeptin-sensitive second enzyme.
- Procathepsin D and pseudocathepsin D could not be fully converted to single-chain enzyme in vitro.
Conclusions:
- Procathepsin D exhibits partial autocatalytic activity, forming pseudocathepsin D.
- A distinct, leupeptin-sensitive enzyme is necessary for complete procathepsin D to single-chain cathepsin D conversion.
- The activation mechanism of procathepsin D is distinct from pepsinogen autoactivation and prorenin conversion.