Inhibition of dipeptidyl aminopeptidase IV (DP-IV) by Xaa-boroPro dipeptides and use of these inhibitors to examine the role of DP-IV in T-cell function.
Dipeptidyl peptidase IV (DP-IV; dipeptidyl-peptide hydrolase, EC 3.4.14.5) is a serine protease with a specificity for cleaving Xaa-Pro dipeptides from polypeptides and proteins. It is found in a variety of mammalian cells and tissues, including those of lymphoid origin where it is found specifically on the surface of CD4+ T cells. Although the functional significance of this enzyme has not been established, a role in T-cell activation and immune regulation has been proposed. Here we report that Ala-boroPro and Pro-boroPro, where boroPro is the alpha-amino boronic acid analog of proline, are potent and specific inhibitors of DP-IV, having Ki values in the nanomolar range. Blocking the N terminus of Ala-boroPro abolishes the affinity of this inhibitor for DP-IV, while removal of the N-terminal residue, to give boroPro, reduces the affinity for DP-IV by 5 orders of magnitude. The dipeptide boronic acids exhibit slow-binding kinetics, while boroPro does not. We also report here that low concentrations of Pro-boroPro inhibit antigen-induced proliferation and interleukin 2 production in murine T-cell lines but do not inhibit the response of these T cells to the mitogen concanavalin A. These results indicate that DP-IV plays a role in antigen-induced, but not mitogen-induced, activation of T lymphocytes.
Flentke
G R
GR
Department of Biochemistry, Tufts University School of Medicine, Boston, MA 02111.
Munoz
E
E
Huber
B T
BT
Plaut
A G
AG
Kettner
C A
CA
Bachovchin
W W
WW
D000818:Animals; D001897:Boronic Acids; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004151:Dipeptides / Q000494:pharmacology*; D018819:Dipeptidyl Peptidase 4; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000037:antagonists & inhibitors*; D007376:Interleukin-2 / Q000096:biosynthesis; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D051379:Mice; D011392:Proline; D013329:Structure-Activity Relationship; D013552:Swine; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology
D001897:Boronic Acids; D004151:Dipeptides; D007376:Interleukin-2; D011392:Proline; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D018819:Dipeptidyl Peptidase 4