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Tartrate-resistant acid phosphatase forms complexes with alpha2-macroglobulin in serum
C S Brehme1, S Roman, J Shaffer
1Department of Skeletal Research, Hybritech Incorporated, a subsidiary of Beckman Coulter, Inc., San Diego, California 92196-9006, USA.
Summary
Tartrate-resistant acid phosphatase (TRAP) in serum forms complexes with alpha2-macroglobulin (alpha2M). This complex formation reduces TRAP activity and immunoreactivity, potentially affecting measurements in patient samples.
Area of Science:
- Biochemistry
- Bone Metabolism
- Clinical Chemistry
Background:
- Tartrate-resistant acid phosphatase (TRAP) is a marker for osteoclast activity.
- Serum TRAP levels are used to assess bone metabolism.
- Current methods for measuring TRAP in serum are inconsistent.
Purpose of the Study:
- To investigate the stability and behavior of TRAP in serum.
- To identify factors contributing to variability in serum TRAP measurements.
- To assess the impact of serum components on TRAP activity and immunoreactivity.
Main Methods:
- Purified TRAP was spiked into serum and analyzed.
- Complex formation was studied using purified components.
- TRAP enzyme activity and immunoreactivity were measured.
- Protein identification was performed using established techniques.
Main Results:
- Purified TRAP formed high molecular weight complexes in serum.
- Complex formation significantly decreased TRAP enzyme activity and immunoreactivity.
- Alpha2-macroglobulin (alpha2M) was identified as the protein responsible for complex formation.
- Similar complexes were observed in stored patient samples.
Conclusions:
- TRAP instability in serum is partly due to complex formation with alpha2M.
- Current TRAP enzyme and immunoassays may not accurately reflect circulating TRAP levels.
- Further research is needed to develop reliable methods for measuring TRAP in biological samples.