Mesentery vascular metabolism of substance P

Dipeptidylpeptidase IV (EC 3.4.14.5), an enzyme which metabolizes substance P, is present in crude homogenates of hog mesenteric artery and aorta. Its subcellular localization is closely correlated with the plasma membrane marker enzyme 5'-nucleotidase (EC 3.1.3.5) in addition to the kinin and angiotensin metabolizing enzymes angiotensin I converting enzyme (EC 3.4.15.1) and aminopeptidase M (EC 3.4.11.2). The highest level of dipeptidylpeptidase IV is found on the surface membrane-enriched fraction and is immunologically identical to the kidney brush border-bound enzyme. Vascular dipeptidylpeptidase IV sequentially removes the N-terminal Arg1-Pro2 and Lys3-Pro4 dipeptides of substance P and exposes the biologically active C-terminal heptapeptide product to rapid degradation by vascular aminopeptidases.