The Crystal Structure of Dipeptidyl Peptidase IV (CD26) Reveals Its Functional Regulation and Enzymatic Mechanism

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 100; no. 9; pp. 5063 - 5068
• Main Authors: Engel, Michael, Hoffmann, Torsten, Wagner, Leona, Wermann, Michael, Heiser, Ulrich, Kiefersauer, Reiner, Huber, Robert, Bode, Wolfram, Demuth, Hans-Ulrich, Brandstetter, Hans
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 29.04.2003; National Acad Sciences; The National Academy of Sciences
• Subjects: Active sites; Amino Acid Sequence; Animals; Atoms; Binding Sites; Biological Sciences; Catalysis; Crystal structure; Crystallography, X-Ray; Dimerization; Dimers; Dipeptidyl Peptidase 4 - chemistry; Dipeptidyl Peptidase 4 - metabolism; DNA, Complementary; Enzymes; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; Propellers; Protease Inhibitors - pharmacology; Protein Conformation; Proteins; Sequence Homology, Amino Acid; Swine; Topology; Tunnels
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0230620100

The membrane-bound glycoprotein dipeptidyl peptidase IV (DP IV, CD26) is a unique multifunctional protein, acting as receptor, binding and proteolytic molecule. We have determined the sequence and 1.8 Å crystal structure of native DP IV prepared from porcine kidney. The crystal structure reveals a 2-2-2 symmetric tetrameric assembly which depends on the natively glycosylated β-propeller blade IV. The crystal structure indicates that tetramerization of DP IV is a key mechanism to regulate its interaction with other components. Each subunit comprises two structural domains, the N-terminal eight-bladed β-propeller with open Velcro topology and the C-terminal α/β-hydrolase domain. Analogy with the structurally related POP and tricorn protease suggests that substrates access the buried active site through the β-propeller tunnel while products leave the active site through a separate side exit. A dipeptide mimicking inhibitor complexed to the active site discloses key determinants for substrate recognition, including a Glu-Glu motif that distinguishes DP IV as an aminopeptidase and an oxyanion trap that binds and activates the P2-carbonyl oxygen necessary for efficient postproline cleavage. We discuss active and nonactive site-directed inhibition strategies of this pharmaceutical target protein.