Phosphorylation of isocarbostyril- and difluorophenyl-nucleoside thymidine mimics by the human deoxynucleoside kinases.
The thymidine mimics isocarbostyril nucleosides and difluorophenyl nucleosides were tested as deoxynucleoside kinase substrates using recombinant human cytosolic thymidine kinase (TK1) and deoxycytidine kinase (dCK), and mitochondrial thymidine kinase (TK2) and deoxyguanosine kinase (dGK). The isocarbostyril nucleoside compound 1-(2-deoxy-beta-D-ribofuranosyl)-isocarbostyril (EN1) was a poor substrate with all the enzymes. The phosphorylation rates of EN1 with TK1 and TK2 were <1% relative to Thd, where as the phosphorylation rates for EN1 were 1.4% and 1.1% with dCK and dGK relative to dCyd and dGuo, respectively. The analogue 1-(2-deoxy-beta-D-ribofuranosyl)-7-iodoisocarbostyril (EN2) showed poor relative-phosphorylation efficiencies (kcat/Km) with both TK1 and dGK, but not with TK2. The kcat/Km value for EN2 with TK2 was 12.6% relative to that for Thd. Of the difluorophenyl nucleosides, 5-(1'-(2'-deoxy-beta-D-ribofuranosyl))-2,4-difluorotoluene (JW1) and 1-(1'-(2'-deoxy-beta-D-ribofuranosyl))-2,4-difluoro-5-iodobenzene (JW2) were substrates for TK1 with phosphorylation efficiencies of about 5% relative to that for Thd. Both analogues were considerably more efficient substrates for TK2, with kcat/Km values of 45% relative to that for Thd. 2,5-Difluoro-4-[1-(2-deoxy-beta-L-ribofuranosyl)]-aniline (JW5), a L-nucleoside mimic, was phosphorylated up to 15% as efficiently as deoxycytidine by dCK. These data provide a possible explanation for the previously reported lack of cytotoxicity of the isocarbostyril- and difluorophenyl nucleosides, but potential mitochondrial effects of EN2, JW1 and JW2 should be further investigated.
Al-Madhoun
Ashraf Said
AS
Division of Cardiology, Vascular Biology Laboratory, University of Ottawa Heart Institute, Ottawa, Canada.
Eriksson
Staffan
S
Wang
Zhi-Xian
ZX
Naimi
Ebrahim
E
Knaus
Edward E
EE
Wiebe
Leonard I
LI
D006801:Humans; D007546:Isoquinolines / Q000138:chemical synthesis*; D018716:Molecular Mimicry; D015394:Molecular Structure; D009705:Nucleosides / Q000138:chemical synthesis*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry*; D013936:Thymidine / Q000031:analogs & derivatives* / Q000138:chemical synthesis*
D007546:Isoquinolines; D009705:Nucleosides; D017853:Phosphotransferases (Alcohol Group Acceptor); C020018:deoxyribonucleoside kinases; D013936:Thymidine