Go Back Dipeptidylpeptidase IV (DDP-4), human

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ipeptidyl peptidase IV (DPPIV) in normal human serum displays a molecular weight of approximately 105000 on SDS-PAGE, almost the same as that of human kidney membrane-bound DPPIV. No difference was found between the two enzymes enzymologically and immunologically, either in substrate specificity, susceptibility to inhibitors, or cross-reactivity with an anti-rat kidney DPP IV antibody, or in their ability to bind adenosine deaminase. However, the N-terminal amino acid sequence of serum DPPIV lacked the transmembrane domain of the membrane-bound enzyme and started at the 39th position, serine, from the N-terminus predicted from the cDNA nucleotide sequence. These results suggest that membrane-bound DPPIV loses its transmembrane domain upon release into the serum, and that its structure on the plasma membrane is not required for its binding to adenosine deaminase.It was observed that anti-tumor necrosis factor-alpha therapy augments dipeptidyl peptidase IV activity and decreases autoantibodies to GRP78/BIP and phosphoglucose isomerase in patient with rheumatoid arthritis. A reduction of serum enzyme activity and its correlation with disease activity in systemic lupus erythematosus was as well as an increased serum activity was reported for patients with inflammatory bowel disease or primary biliary cirrhosis . The presence of soluble dipeptidyl peptidase IV and the diagnostic efficiency and predictive value for colorectal cancer was studied. Experimental and clinical evidence was presented ascribing dipeptidyl peptidase IV enzyme activity in serum and urine to cholestasis.