Tartrate-resistant acid phosphatase type 5 (TRAP (also ACP5))

Tartrate-resistant acid phosphatase type 5 (TRAP, also known as ACP5) is a metalloenzyme and member of the purple acid phosphatase family, expressed primarily in osteoclasts and activated macrophages. It hydrolyzes phosphate esters at acidic pH and is named for its resistance to tartrate inhibition (distinguishing it from other acid phosphatases). TRAP's active site contains a dinuclear iron center essential for catalysis. This enzyme is crucial in bone resorption, where it dephosphorylates bone proteins such as osteopontin and bone sialoprotein, and is implicated in pathological states including Gaucher disease, Hodgkin disease, osteopetrosis, and immune system disorders due to its role in osteoclast and macrophage biology. Serum levels of TRAP5b serve as a clinical biomarker for osteoclast activity and bone turnover. Genetic deficiency of ACP5 leads to spondyloenchondrodysplasia, a multi-system disorder with skeletal and immune manifestations. While not a major direct drug target in current therapy, its role in bone and immune pathophysiology continues to be explored for potential diagnostic and therapeutic applications.

Other names

Acid phosphatase 5tartrate-resistant acid phosphataseACP5TRAPTRAP5bType 5 acid phosphatasepurple acid phosphatase

For candidate inhibitors: Competitive inhibition at the enzyme active site (demonstrated in vitro with fluoride ions). Enzyme acts on a wide variety of phosphate ester substrates via nucleophilic attack and hydrolysis, catalyzed by a di-iron center.