Johansson M, Karlsson A
Medical Nobel Institute, Department of Medical Biochemistry and Biophysics, Karolinska Institute, S-171 77 Stockholm, Sweden.
J Biol Chem. 1997 Mar 28;272(13):8454-8. doi: 10.1074/jbc.272.13.8454.
Human thymidine kinase 2 (TK2) is a deoxyribonucleoside kinase that phosphorylates thymidine, deoxycytidine, and deoxyuridine. The enzyme also phosphorylates anti-viral and anti-cancer nucleoside analogs. We have identified an expressed sequence tag cDNA that encoded a 27.5-kDa protein approximately 30% similar to the human deoxycytidine kinase and deoxyguanosine kinase. The protein was expressed in Escherichia coli and shown to have similar substrate specificity as reported for purified native human TK2. The recombinant TK2 was shown to phosphorylate the anti-cancer nucleoside analog 2',2'-difluorodeoxycytidine. Northern blot analysis showed two mRNA species at 2.4 and 4.0 kilobases predominantly expressed in liver, pancreas, muscle, and brain. We identified a sequence-tagged site designed from the 3' region of the TK2 cDNA. The sequence-tagged site has been mapped to 81-84 centimorgans from the top linkage group of chromosome 16, which corresponds to the 16q22 region. Our data show that deoxycytidine kinase, deoxyguanosine kinase, and TK2 belong to a family of closely related enzymes. At the time of this report all four of the known human deoxyribonucleoside kinases have been cloned. This provides the opportunity to characterize their individual contribution to therapeutic and toxic effects of nucleoside analogs.
人胸苷激酶2（TK2）是一种脱氧核糖核苷激酶，可将胸苷、脱氧胞苷和脱氧尿苷磷酸化。该酶还可将抗病毒和抗癌核苷类似物磷酸化。我们鉴定出一个表达序列标签cDNA，其编码一种27.5 kDa的蛋白质，与人类脱氧胞苷激酶和脱氧鸟苷激酶约有30%的相似性。该蛋白质在大肠杆菌中表达，并显示出与纯化的天然人TK2报道的底物特异性相似。重组TK2显示可将抗癌核苷类似物2'，2'-二氟脱氧胞苷磷酸化。Northern印迹分析显示在2.4和4.0千碱基处有两种mRNA，主要在肝脏、胰腺、肌肉和大脑中表达。我们从TK2 cDNA的3'区域设计了一个序列标签位点。该序列标签位点已定位到16号染色体顶部连锁群81-84厘摩处，对应于16q22区域。我们的数据表明，脱氧胞苷激酶、脱氧鸟苷激酶和TK2属于密切相关的酶家族。在本报告发布时，所有四种已知的人类脱氧核糖核苷激酶均已克隆。这为表征它们对核苷类似物治疗和毒性作用的个体贡献提供了机会。
