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TitleTransition state analogues of plasmodium falciparum and human orotate phosphoribosyltransferases
Publication TypeJournal Article
Year of Publication2013
AuthorsZhang, Y., Evans G.B., Clinch K., Crump D.R., Harris L.D., Fröhlich R.F.G., Tyler P.C., Hazleton K.Z., Cassera M.B., and Schramm V.L.
JournalJournal of Biological Chemistry
Pagination34746 - 34754
Date Published2013
ISSN00219258 (ISSN)
Keywords4 nitrophenyl riboside 5' phosphate, Aromatic compounds, article, binding affinity, Binding energy, binding site, carbon, conformational transition, controlled study, Dissociation, dissociation constant, enzyme active site, enzyme inhibition, Ethylene, Geometry, human, hydrogen bond, Hydrogen bond networks, Hydrogen bonds, iminoribitol, Inhibition constants, nonhuman, Nucleic acids, nucleoside derivative, Nucleoside derivatives, Nucleotide-binding sites, orotate phosphoribosyltransferase, phosphate, Phosphoribosyltransferase, Plasmodium falciparum, priority journal, pyrimidine, ribitol, static electricity, Transition-state analogues, unclassified drug
AbstractThe survival and proliferation of Plasmodium falciparum parasites and human cancer cells require de novo pyrimidine synthesis to supply RNA and DNA precursors. Orotate phosphoribosyltransferase (OPRT) is an indispensible component in this metabolic pathway and is a target for antimalarials and antitumor drugs. P. falciparum (Pf) and Homo sapiens (Hs) OPRTs are characterized by highly dissociative transition states with ribocation character. On the basis of the geometrical and electrostatic features of the PfOPRT and HsOPRT transition states, analogues were designed, synthesized, and tested as inhibitors. Iminoribitol mimics of the ribocation transition state in linkage to pyrimidine mimics using methylene or ethylene linkers gave dissociation constants (Kd) as low as 80 nM. Inhibitors with pyrrolidine groups as ribocation mimics displayed slightly weaker binding affinities for OPRTs. Interestingly, p-nitrophenyl riboside 5'-phosphate bound to OPRTs with Kd values near 40 nM. Analogues designed with a C5-pyrimidine carbon-carbon bond to ribocation mimics gave Kd values in the range of 80-500 nM. Acyclic inhibitors with achiral serinol groups as the ribocation mimics also displayed nanomolar inhibition against OPRTs. In comparison with the nucleoside derivatives, inhibition constants of their corresponding 5'-phosphorylated transition state analogues are largely unchanged, an unusual property for a nucleotide-binding site. In silico docking of the best inhibitor into the HsOPRT active site supported an extensive hydrogen bond network associated with the tight binding affinity. These OPRT transition state analogues identify crucial components of potent inhibitors targeting OPRT enzymes. Despite their tight binding to the targets, the inhibitors did not kill cultured P. falciparum. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.

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