ACP5(acid phosphatase 5, tartrate resistant) is also named as TRAP, TrATPase and belongs to the metallophosphoesterase superfamily. It is an iron-containing glycoprotein with a molecular mass of approximately 34 kD. ACP5 is a histochemical marker of the osteoclast. It is also characteristic of monohistiocytes, particularly alveolar macrophages, and is associated with diverse pathological conditions, including hairy cell leukemia and AIDS encephalopathy.(PMID:10639488).