Tyrosine 547 Constitutes an Essential Part of the Catalytic Mechanism of Dipeptidyl Peptidase IVBjelke, J.R., Christensen, J., Branner, S., Wagtmann, N., Olsen, C., Kanstrup, A.B., Rasmussen, H.B.
(2004) J Biol Chem 279: 34691-34697
- PubMed: 15175333
- DOI: https://doi.org/10.1074/jbc.M405400200
- Primary Citation of Related Structures:
1TK3, 1TKR, 1U8E
- PubMed Abstract:
Human dipeptidyl peptidase IV (DPP-IV) is a ubiquitously expressed type II transmembrane serine protease. It cleaves the penultimate positioned prolyl bonds at the N terminus of physiologically important peptides such as the incretin hormones glucagon-like peptide 1 and glucose-dependent insulinotropic peptide. In this study, we have characterized different active site mutants. The Y547F mutant as well as the catalytic triad mutants S630A, D708A, and H740L showed less than 1% wild type activity. X-ray crystal structure analysis of the Y547F mutant revealed no overall changes compared with wild type apoDPP-IV, except the ablation of the hydroxyl group of Tyr(547) and a water molecule positioned in close proximity to Tyr(547). To elucidate further the reaction mechanism, we determined the crystal structure of DPP-IV in complex with diisopropyl fluorophosphate, mimicking the tetrahedral intermediate. The kinetic and structural findings of the tyrosine residue are discussed in relation to the catalytic mechanism of DPP-IV and to the inhibitory mechanism of the 2-cyanopyrrolidine class of potent DPP-IV inhibitors, proposing an explanation for the specificity of this class of inhibitors for the S9b family among serine proteases.
Institute of Medical Biochemistry and Genetics, Panum Institute, University of Copenhagen, Bledamsvej 3C, DK-2200 Copenhagen, Denmark.