Tartrateresistant

Tartrate-resistant describes a property of certain enzymes that retain activity in the presence of tartrate, a salt derived from tartaric acid. The term is most commonly used for tartrate-resistant acid phosphatase (TRAP), an enzyme produced by osteoclasts and some macrophage-lineage cells. In contrast to tartrate-sensitive phosphatases, TRAP remains active when tartrate is present, a distinction exploited in histochemical staining to identify osteoclasts in bone tissue.

Biochemical and clinical relevance: TRAP is involved in bone resorption and remodeling. The enzyme exists in several isoforms, with TRAP5b often associated with osteoclast activity and bone turnover. Histochemical assays use tartrate-containing buffers to inhibit non-TRAP phosphatases, allowing visualization of tartrate-resistant activity as a colored product in tissue samples.

Clinical significance: Increased TRAP activity or the presence of TRAP-positive osteoclasts can be observed in conditions with high bone turnover, such as Paget disease and various forms of osteoporosis, and in certain malignancies with bone involvement. Serum or tissue TRAP measurements can aid in assessing osteoclast activity, though TRAP is not exclusively specific to a single disease.

Limitations: TRAP is one marker among many for bone metabolism; its levels can be influenced by age, sex, hormones, and systemic illness. Other tartrate-resistant enzymes exist in different tissues and contexts, so interpretation should consider the broader clinical and histological picture.

See also: tartrate-sensitive acid phosphatases, osteoclast, bone remodeling.