Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study demonstrates that the 175-kDa form of dipeptidyl peptidase IV (DPPIV) found in normal human serum is identical with a similarly-sized Ag, DPPT-L, found to be rapidly expressed on the surface of activated T cells. As activation progresses, the expression of DPPT-L reaches a peak on day 3, after which expression falls, whereas expression of the 105-kDa CD26/DPPIV detected by the mAb 1F7 increases, as does the ability to bind adenosine deaminase. The loss of DPPT-L from the surface of activated T cells correlates exactly with the appearance of DPPT-L and DPPIV activity in serum-free tissue culture medium. The release of DPPIV was generally greater from CD4+ cells than from CD8+ T cells, and within the CD4+ subset, the CD45RO+ subset was the major source, which correlated with surface expression before culture. We show that the DPPIV released from activated T cells is antigenically, biochemically, and enzymatically similar to DPPIV circulating in the serum and is distinct from the DPPIV activity of 105-kDa CD26. The T cell-released DPPIV is able to function as a costimulating molecule for the response to the recall Ag, tetanus toxoid, at levels similar to those at which recombinant soluble CD26 and serum DPPIV exhibit costimulatory function, suggesting that the released DPPIV may serve an important immunoregulatory function in vivo, both locally and within the systemic circulation.
 ...
PMID:Serum high molecular weight dipeptidyl peptidase IV (CD26) is similar to a novel antigen DPPT-L released from activated T cells. 859 18

Dipeptidyl peptidase IV (DPPIV, EC 3.4.14.5) is a serine type protease with an important modulatory activity on a number of chemokines, neuropeptides and peptide hormones. It is also known as CD26 or adenosine deaminase (ADA; EC 3.5.4.4) binding protein. DPPIV has been demonstrated on the plasmamembranes of T cells and activated natural killer or B cells as well as on a number of endothelial and differentiated epithelial cells. A soluble form of CD26/DPPIV has been described in serum. Over the past few years, several related enzymes with similar dipeptidyl peptidase activity have been discovered, raising questions on the molecular origin(s) of serum dipeptidyl peptidase activity. Among them attractin, the human orthologue of the mouse mahogany protein, was postulated to be responsible for the majority of the DPPIV-like activity in serum. Using ADA-affinity chromatography, it is shown here that 95% of the serum dipeptidyl peptidase activity is associated with a protein with ADA-binding properties. The natural protein was purified in milligram quantities, allowing molecular characterization (N-terminal sequence, glycosylation type, CD-spectrum, pH and thermal stability) and comparison with CD26/DPPIV from other sources. The purified serum enzyme was confirmed as CD26.
 ...
PMID:Molecular characterization of dipeptidyl peptidase activity in serum: soluble CD26/dipeptidyl peptidase IV is responsible for the release of X-Pro dipeptides. 1095 Dec 21