RT Journal Article
SR Electronic
T1 Human Mitochondrial Thymidine Kinase Is Selectively Inhibited by 3′-Thiourea Derivatives of β-Thymidine: Identification of Residues Crucial for Both Inhibition and Catalytic Activity
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1127
OP 1136
DO 10.1124/mol.108.053785
VO 75
IS 5
A1 Jan Balzarini
A1 Ineke Van Daele
A1 Ana Negri
A1 Nicola Solaroli
A1 Anna Karlsson
A1 Sandra Liekens
A1 Federico Gago
A1 Serge Van Calenbergh
YR 2009
UL http://molpharm.aspetjournals.org/content/75/5/1127.abstract
AB Substituted 3′-thiourea derivatives of β-thymidine (dThd) and 5′-thiourea derivatives of α-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 β-dThd proved highly inhibitory to and selective for TK-2 (IC50 value, 0.15-3.1 μM). The 3′-C-branched p-methylphenyl (compound 1) and 3-CF3-4-Cl-phenyl (compound 7) thiourea derivatives of β-dThd showed competitive inhibition of TK-2 when dThd was used as the variable substrate (Ki values, 0.40 and 0.05 μM, respectively), but uncompetitive inhibition in the presence of variable concentrations of ATP (Ki values, 15 and 2.0 μM, 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 γ-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 Ki/Km 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. The American Society for Pharmacology and Experimental Therapeutics