Title: Human mitochondrial thymidine kinase is selectively inhibited by 3 '-thiourea derivatives of beta-thymidine: identification of residues crucial for both inhibition and catalytic activity
Authors: Balzarini, Jan ×
Van Daele, Ineke
Negri, Ana
Solaroli, Nicola
Karlsson, Anna
Liekens, Sandra
Gago, Federico
Van Calenbergh, Serge #
Issue Date: May-2009
Publisher: American Society for Pharmacology and Experimental Therapeutics
Series Title: Molecular Pharmacology vol:75 issue:5 pages:1127-1136
Abstract: Substituted 3'-thiourea derivatives of beta-thymidine (dThd) and 5'-thiourea derivatives of alpha-dThd have been evaluated for their inhibitory activity against recombinant human cytosolic dThd kinase-1 (TK-1), human mitochondrial TK-2, herpes simplex virus type 1 (HSV-1) TK, and varicella-zoster virus TK. Several substituted 3'-thiourea derivatives of beta-dThd proved highly inhibitory to and selective for TK-2 (IC50 value, 0.15-3.1 mu M). The 3'-C-branched p-methylphenyl (compound 1) and 3-CF3-4-Cl-phenyl (compound 7) thiourea derivatives of beta-dThd showed competitive inhibition of TK-2 when dThd was used as the variable substrate (K-i values, 0.40 and 0.05 mu M, respectively), but uncompetitive inhibition in the presence of variable concentrations of ATP (K-i values, 15 and 2.0 mu M, respectively). These kinetic properties of compounds 1 and 7 against TK-2 could be accounted for by molecular modeling showing that two hydrogen bonds can be formed between the thiourea nitrogens of compound 7 and the oxygens of the gamma-phosphate of ATP. The importance of several active-site residues was assessed by site-directed mutagenesis experiments on TK-2 and the related HSV-1 TK. The low K-i/K-m ratios for compounds 1 and 7 (0.38 and 0.039 against dThd, and 0.75 and 0.12 against ATP, respectively) indicate that these compounds are among the most potent inhibitors of TK-2 described so far. In addition, a striking close correlation was found between the inhibitory activities of the test compounds against TK-2 and Mycobacterium tuberculosis thymidylate kinase that is strongly indicative of close structural and/or functional similarities between both enzymes in relation to their mode of interaction with these nucleoside analog inhibitors.
ISSN: 0026-895X
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Laboratory of Virology and Chemotherapy (Rega Institute)
× corresponding author
# (joint) last author

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