title: Deoxyribonucleoside kinases belonging to the thymidine kinase 2 (TK2)-like group vary significantly in substrate specificity, kinetics and feed-back regulation.
abstract: In eukaryotic cells deoxyribonucleoside kinases belonging to three phylogenetic sub-families have been found: (i) thymidine kinase 1 (TK1)-like enzymes, which are strictly pyrimidine deoxyribonucleoside-specific kinases; (ii) TK2-like enzymes, which include pyrimidine deoxyribonucleoside kinases and a single multisubstrate kinase from Drosophila melanogaster (Dm-dNK); and (iii) deoxycytidine/deoxyguanosine kinase (dCK/dGK)-like enzymes, which are deoxycytidine and/or purine deoxyribonucleoside-specific kinases. We cloned and characterized two new deoxyribonucleoside kinases belonging to the TK2-like group from the insect Bombyx mori and the amphibian Xenopus laevis. The deoxyribonucleoside kinase from B. mori (Bm-dNK) turned out to be a multisubstrate kinase like Dm-dNK. But uniquely for a deoxyribonucleoside kinase, Bm-dNK displayed positive cooperativity with all four natural deoxyribonucleoside substrates. The deoxyribonucleoside kinase from X. laevis (Xen-PyK) resembled closely the human and mouse TK2 enzymes displaying their characteristic Michaelis-Menten kinetic with deoxycytidine and negative cooperativity with its second natural substrate thymidine. Bm-dNK, Dm-dNK and Xen-PyK were shown to be homodimers. Significant differences in the feedback inhibition by deoxyribonucleoside triphosphates between these three enzymes were found. The insect multisubstrate deoxyribonucleoside kinases Bm-dNK and Dm-dNK were only inhibited by thymidine triphosphate, while Xen-PyK was inhibited by thymidine and deoxycytidine triphosphate in a complex pattern depending on the deoxyribonucleoside substrate. The broad substrate specificity and different feedback regulation of the multisubstrate insect deoxyribonucleoside kinases may indicate that these enzymes have a different functional role than the other members of the TK2-like group.
authors.affiliation: Section of Molecular Microbiology, BioCentrum-DTU, Building 301, Technical University of Denmark, Lyngby, DK 2800, Denmark. wolfgang.knecht@biocentrum.dtu.dk
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Knecht
authors.forename: Gitte Ebert
authors.initials: GE
authors.lastname: Petersen
authors.forename: Birgitte
authors.initials: B
authors.lastname: Munch-Petersen
authors.forename: Jure
authors.initials: J
authors.lastname: Piskur
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000201:enzymology* / Q000235:genetics; D002645:Chickens; D002850:Chromatography, Gel; D030541:Databases, Genetic; D003841:Deoxycytidine / Q000378:metabolism; D004331:Drosophila melanogaster / Q000201:enzymology; D025461:Feedback, Physiological; D006801:Humans; D020128:Inhibitory Concentration 50; D007700:Kinetics; D051379:Mice; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D020836:Protein Structure, Quaternary; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics; D013379:Substrate Specificity; D013937:Thymidine Kinase / Q000737:chemistry*; D014982:Xenopus laevis / Q000235:genetics*
chemical_list: D011993:Recombinant Fusion Proteins; D003841:Deoxycytidine; D017853:Phosphotransferases (Alcohol Group Acceptor); C020018:deoxyribonucleoside kinases; C105339:thymidine kinase 2; D013937:Thymidine Kinase