TRAP 5 (serum band 5 tartrate-resistant acid phosphatase, TRACP 5; EC 3.1.3.2) is a glycoprotein of 35–37 kDa. TRAP 5 belongs to the most abundant enzymes in osteoclasts. It is expressed in certain differentiated cells of the mononuclear phagocyte system, particularly osteoclasts and alveolar macrophages, where it takes an active part in bone resorption process. High blood levels of TRAP 5 are usually associated with active bone remodelling. Increased serum levels are observed during normal bone growth among healthy children. Elevated serum TRAP levels have been detected in diseases characterized by increased bone resorption; Paget’s disease of the bone, hemodialysis, primary hyperparathyroidism, metastatic malignancies involving bone resorption, multiple myeloma and bilaterally ovariectomized women. Post-menopausal women have higher levels of serum than post-menopausal women on estrogen replacement therapy. Therefore specific determination of TRAP 5 activity can be essential for clinical assessment of bone metabolism.
- References to TRAP 5 (TRACP 5, Tartrate Resistant Acid Phosphatase 5)