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Human platelet heparanase: purification, characterization and catalytic activity
1Division of Immunology and Cell Biology, John Curtin School of Medical Research, Australian National University, Canberra, ACT2601, Australia. Craig.Freeman@anu.edu.au
The Biochemical Journal
|May 23, 1998
Summary
Platelet heparanase, an enzyme that degrades heparan sulphate (HS), was purified and characterized. This enzyme may aid cancer cell migration by breaking down the extracellular matrix, and inhibitors could block this process.
Area of Science:
- Biochemistry
- Molecular Biology
- Extracellular Matrix Research
Background:
- Heparan sulphate (HS) in the extracellular matrix (ECM) and basal lamina (BL) inhibits cell migration.
- Platelet activation during cancer cell aggregation releases heparanase, potentially aiding metastasis.
- Understanding platelet heparanase is crucial for developing anti-metastatic strategies.
Purpose of the Study:
- To purify and characterize human platelet heparanase.
- To investigate the enzyme's role in degrading HS and heparin.
- To explore substrate specificity and inhibition mechanisms.
Main Methods:
- Purification of human platelet heparanase using a five-column chromatography procedure.
- Enzyme activity assay for HS degradation.
- Analysis of molecular mass by gel filtration and SDS-PAGE.
- Substrate specificity studies using modified heparin analogues.
- Inhibition studies with heparin analogues.
Main Results:
- Human platelet heparanase purified 1700-fold to homogeneity.
- The enzyme is a 50 kDa endoglucuronidase that degrades HS and heparin into smaller fragments.
- Substrate cleavage requires carboxyl groups; O-sulphation is essential for inhibition.
- Inhibitors of tumour heparanase also inhibit platelet heparanase.
Conclusions:
- Platelet heparanase plays a role in ECM and BL degradation, facilitating cell migration.
- Heparin analogues inhibiting tumour heparanase may also prevent platelet heparanase activity.
- Targeting platelet heparanase with specific inhibitors presents a potential anti-metastatic therapy.