Shiotani T, Hashimoto Y, Tanaka T, Irino S
First Department of Internal Medicine, Kagawa Medical School, Japan.
Cancer Res. 1989 Mar 1;49(5):1090-4.
The behavior of the activities of thymidine metabolizing enzymes, dihydrothymine dehydrogenase (EC 1.3.1.2) and thymidine phosphorylase (EC 2.4.2.4) for thymidine degradation, thymidine kinase (EC 2.7.1.75) and thymidylate synthase (EC 2.1.1.45) for DNA synthesis, was elucidated in cytosolic extracts from normal human lymphocytes and 13 human leukemia-lymphoma cell lines. In the normal human lymphocytes, the activities of dihydrothymine dehydrogenase, thymidine phosphorylase, thymidine kinase, and thymidylate synthase were 6.88, 796, 0.30, and 0.29 nmol/h/mg protein, respectively. In leukemia-lymphoma cell lines, the activities of synthetic enzymes, thymidine kinase, and thymidylate synthase, increased two- to 79-fold and 22- to 407-fold of the normal lymphocyte values. In contrast, the activities of the catabolic enzymes, dihydrothymine dehydrogenase and thymidine phosphorylase, decreased to 5-42% and 3-38% of the values of normal lymphocytes. As a result, the ratio of activities of thymidine kinase/dihydrothymine dehydrogenase was elevated by 7- to 1170-fold, respectively. Thus, reciprocal behavior in the activities of the opposing enzymes in thymidine metabolism was observed in human leukemia-lymphoma cells. Polyclonal and monoclonal antibodies against dihydrothymine dehydrogenase were prepared and studies on immunotitration of this enzyme with these antibodies showed that the enzyme protein amount in Jurkat leukemic cells was 36% of that of normal lymphocytes. This was in good agreement with the decrease in the activity of the enzyme to 32%, indicating that the decrease in activity in the leukemic cells was due to the decline in the amount of enzyme protein. The metabolic imbalances in thymidine utilization appear to be characteristic of human leukemia-lymphoma cells. These observations should confer selective advantages to the lymphoproliferating cells and mark out the catabolic, as well as the synthetic, enzymes as important targets in the design of chemotherapy.
在正常人淋巴细胞和13种人类白血病 - 淋巴瘤细胞系的胞质提取物中，对参与胸苷代谢的酶的活性进行了研究。这些酶包括用于胸苷降解的二氢胸腺嘧啶脱氢酶（EC 1.3.1.2）和胸苷磷酸化酶（EC 2.4.2.4），以及用于DNA合成的胸苷激酶（EC 2.7.1.75）和胸苷酸合成酶（EC 2.1.1.45）。在正常人淋巴细胞中，二氢胸腺嘧啶脱氢酶、胸苷磷酸化酶、胸苷激酶和胸苷酸合成酶的活性分别为6.88、796、0.30和0.29 nmol/h/mg蛋白质。在白血病 - 淋巴瘤细胞系中，合成酶胸苷激酶和胸苷酸合成酶的活性比正常淋巴细胞值增加了2至79倍和22至407倍。相反，分解代谢酶二氢胸腺嘧啶脱氢酶和胸苷磷酸化酶的活性降至正常淋巴细胞值的5 - 42%和3 - 38%。结果，胸苷激酶/二氢胸腺嘧啶脱氢酶的活性比分别提高了7至1170倍。因此，在人类白血病 - 淋巴瘤细胞中观察到了胸苷代谢中相反酶活性的相互作用。制备了针对二氢胸腺嘧啶脱氢酶的多克隆和单克隆抗体，用这些抗体对该酶进行免疫滴定研究表明，Jurkat白血病细胞中该酶蛋白量是正常淋巴细胞酶蛋白量的36%。这与酶活性降至32%非常吻合，表明白血病细胞中酶活性的降低是由于酶蛋白量的减少。胸苷利用中的代谢失衡似乎是人类白血病 - 淋巴瘤细胞的特征。这些观察结果应为淋巴细胞增殖细胞赋予选择性优势，并将分解代谢酶和合成酶标记为化疗设计中的重要靶点。
