Characterization of two new variants of human catechol O-methyltransferase in vitro.
Characterization of two new variants of human catechol O-methyltransferase in vitro.
复制标题
人儿茶酚 O-甲基转移酶的两种新变体的体外表征。
DOI：
10.1016/j.canlet.2004.12.022
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Bolton,JudyL
中科院分区：
文献类型：
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作者：
Li,Yan;Yang,Xiaofeng;vanBreemen,RichardB;Bolton,JudyL
邻苯二酚O-甲基转移酶（COMT）在生物活性和毒性邻苯二酚的失活中发挥着重要作用。已经表明，人可溶性COMT（S-COMT）具有野生型和至少一种变体的遗传多态性，其中在密码子108处缬氨酸被甲硫氨酸取代。由于COMT在儿茶酚胺和儿茶酚雌激素代谢中的重要作用，这种多态性一直是分子流行病学研究的主题。几项流行病学研究表明，Val 108 Met变异纯合子的女性患雌激素相关癌症的风险增加。然而，其他一些研究表明，这种COMT多态性与癌症风险增加无关。这些相互矛盾的数据表明，额外的COMT遗传变异可能导致癌症风险增加。虽然最近发现了两个新的单核苷酸多态性（SNP），导致氨基酸取代Ala 22 Ser和Ala 52 Thr，但它们尚未完全表征。在本研究中，使用重组DNA技术产生人S-COMT的Ala 22 Ser和Ala 52 Thr变体，然后测量COMT性质，包括酶活性、热稳定性和对4-羟基马钱宁（4-OHEN）介导的抑制的敏感性。Ala 22 Ser变异体表现出较低的甲基化能力和较高的热不稳定性。此外，该变体对4-OHEN介导的不可逆抑制敏感。我们的数据表明，Ala 22 Ser多态性也可能具有功能意义，并可能在雌激素相关癌症的易感性中发挥作用。
Catechol O-methyltransferase (COMT) plays an important role in the inactivation of biologically active and toxic catechols. It has been shown that human soluble COMT (S-COMT) is genetically polymorphic with a wild type and at least one variant in which a valine has been substituted with a methionine at codon 108. This polymorphism has been the subject of intense molecular epidemiological studies because of the important role of COMT in the metabolism of catecholamines and catechol estrogens. Several epidemiological studies have shown that women, homozygous with the Val108Met variant, have an increased risk of developing estrogen-associated cancers. However, some other studies have shown that this COMT polymorphism is not associated with increased risk of developing cancers. These conflicting data suggest that additional COMT genetic variants might contribute to the increased risk of developing cancers. Although two new single nucleotide polymorphisms (SNP) that cause amino acid substitutions Ala22Ser and Ala52Thr have been identified recently, they have not been fully characterized. In the present study, Ala22Ser and Ala52Thr variants of human S-COMT were produced using recombinant DNA techniques, and then COMT properties were measured including enzymatic activity, thermostability, and sensitivity to inhibition mediated by 4-hydroxyequilenin (4-OHEN). The Ala22Ser variant showed lower methylation capacity and higher thermolability. In addition, this variant is sensitive to 4-OHEN mediated irreversible inhibition. Our data indicate that the Ala22Ser polymorphism might also be of functional significance and might play a role in susceptibility to estrogen-associated cancers.