Differential catalytic efficiency of allelic variants of human glutathione S-transferase Pi in catalyzing the glutathione conjugation of thiotepa
Differential catalytic efficiency of allelic variants of human glutathione S-transferase Pi in catalyzing the glutathione conjugation of thiotepa
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DOI：
10.1006/abbi.1999.1217
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发表时间：
1999-06-01
影响因子：
3.9
通讯作者：
Singh, SV
中科院分区：
文献类型：
--
作者：
Srivastava, SK;Singhal, SS;Singh, SV
烷化剂广泛用于治疗癌症。然而，这类抗癌药物的临床用途往往受到耐药肿瘤细胞出现的限制。谷胱甘肽S-转移酶（GSH-S-transferases，GSTs）催化谷胱甘肽（glutathione，GSH）结合增加被认为是肿瘤细胞对烷化剂耐药的重要机制。在本研究中，我们报告了人类Pi类GST（hGSTP 1 -1）的等位基因变体，其不同之处在于：在位置104和/或113的氨基酸处的一级结构中，其在烷基化抗癌药物噻替派的GSH缀合中的活性表现出显着差异。质谱分析显示，塞替派和GSH之间的反应的主要产物是单谷胱甘肽-塞替派缀合物。虽然单谷胱甘肽-噻替派的非酶促形成可以忽略不计，但在hGSTP 1 -1蛋白存在下，该缀合物的形成显著增加。hGSTP 1 -1催化的谷胱甘肽结合塞替派是时间和蛋白依赖性的，并遵循Michaelis-Menten动力学。hGSTP 1 -1（I104，A113）变体的催化效率分别比hGSTP 1 -1（V104，A113）和hGSTP 1 - 1（V104，V113）同种型高约1.9倍和2.6倍。本研究的结果表明，hGSTP 1 -1多态性可能是GST介导的肿瘤细胞对塞替派耐药的重要因素，hGSTP 1 -1（I104，A113）等位基因纯合子（在人群中最常见）受试者发生GST介导的塞替派耐药的风险可能高于杂合子或具有缬氨酸104背景的纯合子。(C)北京：科学出版社.
Alkylating agents are extensively used in the treatment of cancer. The clinical usefulness of this class of anticancer drugs, however, is often limited by the emergence of drug-resistant tumor cells. Increased glutathione (GSH) conjugation through catalysis by GSH S-transferases (GSTs) is believed to be an important mechanism in tumor cell resistance to alkylating agents. In the present study, we report that the allelic variants of human Pi class GST (hGSTP1-1), which differ: in their primary structures at amino acids in positions 104 and/or 113, exhibit significant differences in their activity in the GSH conjugation of alkylating anticancer drug thiotepa. Mass spectrometry revealed that the major product of the reaction between thiotepa and GSH was the monoglutathionyl-thiotepa conjugate. While nonenzymatic formation of monoglutathionyl-thiotepa was negligible, the formation of this conjugate was increased significantly in the presence of hGSTP1-1 protein. The hGSTP1-1-catalyzed GSH conjugation of thiotepa was time and protein dependent and followed Michaelis-Menten kinetics. The catalytic efficiency of hGSTP1-1(I104,A113) variant was approximately 1.9- and 2.6-fold higher compared with hGSTP1-1(V104,A113) and hGSTP1-1(V104,V113) isoforms, respectively. The results of the present study indicate that the hGSTP1-1 polymorphism may be an important factor in GST-mediated tumor cell resistance to thiotepa, and that subjects homozygous for the hGSTP1-1(I104,A113) allele, which is most frequent in human populations, are likely to be at a greater risk for developing GST-mediated resistance to thiotepa than heterozygotes or homozygotes with valine 104 background. (C) 1999 Academic Press.