Influence of quinone methide reactivity on the alkylation of thiol and amino groups in proteins: studies utilizing amino acid and peptide models
Influence of quinone methide reactivity on the alkylation of thiol and amino groups in proteins: studies utilizing amino acid and peptide models
复制标题
DOI：
10.1016/s0009-2797(97)00079-3
复制
发表时间：
1997-11-28
影响因子：
5.1
通讯作者：
Thompson, JA
中科院分区：
文献类型：
--
作者：
Bolton, JL;Turnipseed, SB;Thompson, JA
醌甲基化物（QMs）是在几种生物过程中形成的亲电体，包括细胞色素P450直接氧化4-烷基酚。这些物种可能是负责某些酚类化合物通过蛋白质烷基化的不利影响，但很少有关于特定的目标或由此产生的细胞损伤机制的信息。目前的目标是确定最有可能的网站之间的竞争蛋白质亲核试剂利用不同亲电性的量子力学的加合物形成。反应性差、反应性中等和反应性高的QM、2，6-二叔丁基-4-亚甲基-2，5-环己二烯酮（BHT-QM）、6-叔丁基-2-亚甲基-2，5-环己二烯酮（BHT-QM）和6-叔丁基-2-亚甲基-2，5-环己二烯酮（BHT-QM）的反应。（2 '-羟基-1'，1 '-二甲基乙基）-4-亚甲基-2，5-环己二烯酮（BHTOH-QM）和2-叔丁基-6-甲基-4-亚甲基-2，5-环己二烯酮（BDMP-QM），在水溶液中与亲核氨基酸。每个QM快速形成半胱氨酸的硫醚衍生物，几乎没有或没有来自水的加入的竞争（水合）。α-氨基是所有其他氨基酸（包括赖氨酸、组氨酸、酪氨酸和丝氨酸）烷基化的主要位点，并且假一级速率是水合速率的5至8倍。赖氨酸和组氨酸的侧链氮的烷基化发生在BDMP-QM的水合速率的约四分之一处，但是对于BHT-QM没有检测到反应，并且QM和氨基酸羟基之间没有发生反应。结果表明，基于化学反应性，肽烷基化应按照半胱氨酸巯基> N-末端氨基> N ε-赖氨酸= NIm-组氨酸的顺序发生，侧链修饰仅发生在更亲电的QM上。QM与三肽Gly-His-lys的反应证实了氨基酸的结果，因为N α-甘氨酸烷基化占主导地位，但也与BHTOH-QM和BDMP-QM形成侧链加合物。人血红蛋白用QMs处理，水解，并通过HPLC-热喷雾质谱法测定。这项工作揭示了NE-赖氨酸是主要的烷基化位点，强调了除了化学反应性之外，影响亲电试剂修饰蛋白质的因素的重要性。(C)1997 Elsevier Science爱尔兰有限公司
Quinone methides (QMs) are electrophiles formed in several biological processes including direct oxidations of 4-alkylphenols by cytochromes P450. These species may be responsible for the adverse effects of certain phenolic compounds through protein alkylation, but little information is available concerning specific targets or the resulting mechanisms of cell injury. The present goal was to determine the most likely sites of adduct formation among competing protein nucleophiles utilizing QMs of varying electrophilicity. Reactions of poorly reactive, moderately reactive, and highly reactive QMs, 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone (BHT-QM), 6-tert-butyl-2-(2'-hydroxy-1',1'-dimethylethyl)-4-methylene-2,5-cyclohexadienone (BHTOH-QM), and 2-tert-butyl-6-methyl-4-methylene-2,5-cyclohexadienone (BDMP-QM), respectively, were investigated in aqueous solutions with nucleophilic amino acids. Each QM rapidly formed a thioether derivative of cysteine with little or no competition from the addition of water (hydration). The a-amino groups were the primary sites of alkylation for all other amino acids examined including lysine, histidine, tyrosine, and serine, and the pseudo-first order rates were 5 to 8-fold greater than the rates of hydration. Alkylation of the side chain nitrogens of lysine and histidine occurred at about one-fourth the rate of hydration for BDMP-QM, but no reaction was detectable for BHT-QM and no reactions occurred between QMs and amino acid hydroxyl groups. The results indicate that, based on chemical reactivity, peptide alkylation should occur in the order cysteine thiol > N-terminal amino > N epsilon-lysine = NIm-histidine, with side chain modifications occurring only with the more electrophilic QMs. Reactions of QMs with the tripeptide Gly-His-lys confirmed the results with amino acids as N alpha-glycine alkylation predominated, but side chain adducts also formed with BHTOH-QM and BDMP-QM. Human hemoglobin was treated with QMs, hydrolyzed, and assayed by HPLC-thermospray mass spectrometry. This work revealed that NE-lysine was the main alkylation site, emphasizing the importance of factors, in addition to chemical reactivity, which influence protein modification by electrophiles. (C) 1997 Elsevier Science Ireland Ltd.