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Testican in human blood
M A BaSalamah1, H S Marr, A W Duncan
1Pathology & Laboratory Medicine Department, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7525, USA.
Biochemical and Biophysical Research Communications
|May 18, 2001
Summary
Researchers identified a 130-kDa testican protein in human plasma, larger than expected due to glycosylation. This unstable plasma form is converted to smaller sizes by protease inhibitors, suggesting a role in blood protease regulation.
Area of Science:
- Biochemistry
- Molecular Biology
- Proteomics
Background:
- Testican is a conserved gene product with an unknown function.
- It is expressed by human endothelial cells and contains a signal sequence.
- This suggests testican protein may be present in blood.
Purpose of the Study:
- To investigate the presence and characteristics of testican protein in human plasma.
- To understand the post-translational modifications and stability of plasma testican.
- To explore the potential function of testican in the blood, possibly related to protease activity.
Main Methods:
- Development of chicken antibodies specific for a near N-terminal testican sequence.
- Identification and characterization of testican protein in human plasma using these antibodies.
- Analysis of recombinant testican for post-translational modifications like glycosylation.
- Investigation of testican stability in plasma and the factors influencing its conversion to smaller forms.
Main Results:
- A 130-kDa form of testican was identified in human plasma, larger than its calculated molecular weight.
- This larger form suggests glycosylation, with recombinant testican showing chondroitin sulfate addition.
- The 130-kDa plasma testican is unstable and converted to smaller forms by plasma factors.
- These conversion factors can be inhibited by serine protease inhibitors.
Conclusions:
- Testican circulates in human plasma as a large, glycosylated form.
- Plasma testican undergoes size conversion mediated by protease activity.
- Testican's homology to protease inhibitors suggests a role in regulating blood proteases.