Structures of the human orotidine-5'-monophosphate decarboxylase support a covalent mechanism and provide a framework for drug design.
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Wittmann JG, Heinrich D, Gasow K, Frey A, Diederichsen U, Rudolph MG
Structures of the human orotidine-5'-monophosphate decarboxylase support a covalent mechanism and provide a framework for drug design.
Structure. 2008 Jan;16(1):82-92. doi: 10.1016/j.str.2007.10.020.
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- 18184586 [ View in 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.