Structures of the human orotidine-5'-monophosphate decarboxylase support a covalent mechanism and provide a framework for drug design.Wittmann, J.G., Heinrich, D., Gasow, K., Frey, A., Diederichsen, U., Rudolph, M.G.
(2008) Structure 16: 82-92
- PubMed: 18184586
- DOI: https://doi.org/10.1016/j.str.2007.10.020
- Primary Citation of Related Structures:
2QCC, 2QCD, 2QCE, 2QCF, 2QCG, 2QCH, 2QCL, 2QCM, 2QCN
- PubMed Abstract:
UMP synthase (UMPS) catalyzes the last two steps of de novo pyrimidine nucleotide synthesis and is a potential cancer drug target. The C-terminal domain of UMPS is orotidine-5'-monophosphate decarboxylase (OMPD), a cofactor-less yet extremely efficient enzyme. Studies of OMPDs from micro-organisms led to the proposal of several noncovalent decarboxylation mechanisms via high-energy intermediates. We describe nine crystal structures of human OMPD in complex with substrate, product, and nucleotide inhibitors. Unexpectedly, simple compounds can replace the natural nucleotides and induce a closed conformation of OMPD, defining a tripartite catalytic site. The structures outline the requirements drugs must meet to maximize therapeutic effects and minimize cross-species activity. Chemical mimicry by iodide identified a CO(2) product binding site. Plasticity of catalytic residues and a covalent OMPD-UMP complex prompt a reevaluation of the prevailing decarboxylation mechanism in favor of covalent intermediates. This mechanism can also explain the observed catalytic promiscuity of OMPD.
Department of Molecular Structural Biology, University of Göttingen, Göttingen, Germany.