Role of 5′-nucleotidase in thiopurine metabolism:: Enzyme kinetic profile and association with thio-GMP levels in patients with acute lymphoblastic leukemia during 6-mercaptopurine treatment
Role of 5′-nucleotidase in thiopurine metabolism:: Enzyme kinetic profile and association with thio-GMP levels in patients with acute lymphoblastic leukemia during 6-mercaptopurine treatment
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DOI：
10.1016/j.cccn.2005.05.006
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发表时间：
2005-11-01
影响因子：
5
通讯作者：
De Abreu, RA
中科院分区：
文献类型：
--
作者：
Brouwer, C;Vogels-Mentink, TM;De Abreu, RA
硫嘌呤用于治疗多种疾病。细胞毒性由衍生化合物6-硫代鸟嘌呤核苷酸（TGN）和甲基-6-硫代肌苷单磷酸（甲硫基-IMP）引起。6-硫代嘌呤单核苷酸6-硫代-IMP（thio-IMP）、6-硫代-GMP（thio-GMP）和甲硫基-IMP可被嘌呤5 '-核苷酸酶分解代谢。已经表明，各种5 '-核苷酸酶是（6-硫代）-嘌呤代谢的关键酶。我们的目的是调查是否整体5 '-核苷酸酶（5' NT）的活性与6-硫嘌呤核苷酸的疗效和毒性。在人淋巴细胞中研究了5 'NT对IMP、GMP、AMP、thio-IMP、thio-GMP和methylthio-IMP的底物亲和力。对于每种底物，最佳总酶活性的pH值已确定在6至10的pH范围内。在最佳pH下，进行测定以确定K-m和V-max值。各种底物的最佳pH值在7和8.5之间。K-m值范围为33 - 109 μ M，V-max范围为3.99 - 19.5 nmol/10（6）外周单核细胞（pMNC）h，V-max/K-m比值范围为105 - 250。结果没有显示出对任何测试的硫嘌呤核苷酸的5 'NT活性的明显偏好。酶动力学研究进一步揭示了作为底物的硫代-IMP和硫代-GMP的底物抑制。硫代GMP的抑制似乎也发生在接受6-巯基嘌呤（6 MP）治疗的患者中;随后，这可能导致这些患者的毒性。(c)2005 Elsevier B.V保留所有权利。
Thiopurines are used for treatment of several diseases. Cytotoxicity is caused by the derived compounds 6-thioguanine nucleotides (TGNs) and methyl-6-thioinosine monophosphate (methylthio-IMP). The 6-thiopurine mononucleotides 6-thio-IMP (thio-IMP), 6-thio-GMP (thio-GMP) and methylthio-IMP can be catabolized by purine 5'-nucleotidase. It has been shown that the various 5'-nucleotidases are key enzymes for (6-thio)-purine metabolism. We aimed to investigate whether the overall 5'-nucleotidase (5'NT) activity is correlated with the efficacy and toxicity of 6-thiopurine nucleotides. Substrate affinity of 5'NT for IMP, GMP, AMP, thio-IMP, thio-GMP and methylthio-IMP was studied in human lymphocytes. For each of the substrates, the pH for optimal overall enzyme activity has been determined at a pH range between 6 and 10. At the optimal pH, assays were performed to establish K-m and V-max values. Optimal pH values for the various substrates were between 7 and 8.5. K-m values ranged from 33 to 109 mu M, V-max ranged from 3.99 to 19.5 nmol/10(6) peripheral mononuclear cells (pMNC) h, and V-max/K-m ratios ranged from 105 to 250. The results did not show a distinct preference of 5'NT activity for any of the tested thiopurine nucleotides. The enzyme kinetic studies furthermore revealed substrate inhibition by thio-IMP and thio-GMP as a substrate. Inhibition by thio-GMP also seems to occur in patients treated with 6-mercaptopurine (6 MP); subsequently, this may lead to toxicity in these patients. (c) 2005 Elsevier B.V All rights reserved.