Chen L J, Hecht S S, Peterson L A
Division of Chemical Carcinogenesis, American Health Foundation, Valhalla, New York 10595, USA.
Chem Res Toxicol. 1997 Aug;10(8):866-74. doi: 10.1021/tx9700174.
Metabolic activation of the hepatocarcinogen furan yields metabolites that react covalently with proteins. cis-2-Butene-1,4-dial is a microsomal metabolite of furan. This reactive aldehyde is thought to be the toxic metabolite that is responsible for the carcinogenic activity of furan. In order to characterize the chemistry by which this unsaturated dialdehyde could alkylate proteins, the products formed upon reaction of cis-2-butene-1,4-dial with model nucleophiles in pH 7.4 buffer were investigated. N(alpha)-Acetyl-L-lysine (AcLys) reacts with cis-2-butene-1,4-dial to form N-substituted pyrrolin-2-one adducts. N-Acetyl-L-cysteine (AcCys) reacts rapidly with cis-2-butene-1,4-dial to form multiple uncharacterized products. The inclusion of AcLys in this reaction mixture yielded an N-substituted 3-(S-acetylcysteinyl)pyrrole adduct which links the two amino acid residues. Related compounds were isolated when cis-2-butene-1,4-dial and glutathione (GSH) were combined. In this case, cis-2-butene-1,4-dial cross-linked two molecules of GSH resulting in either cyclic or acyclic adducts depending on the relative GSH concentration. Incubation of furan with rat liver microsomes in the presence of [glycine-2-3H]GSH led to the formation of radioactive peaks that coeluted with synthetic standards for the bisgluthathione conjugates. These studies demonstrate that the reactive cis-2-butene-1,4-dial formed during the microsomal oxidation of furan reacts rapidly and completely with amino acid residues to form pyrrole and pyrrolin-2-one derivatives. Therefore, this metabolite is a likely candidate for the activated furan derivative that binds to proteins. The ease with which cis-2-butene-1,4-dial cross-links amino acids suggests that pyrrole-thiol cross-links may be involved in the toxicity observed following furan exposure.
肝癌致癌物呋喃的代谢活化产生与蛋白质发生共价反应的代谢产物。顺式-2-丁烯-1,4-二醛是呋喃的一种微粒体代谢产物。这种具有反应活性的醛被认为是导致呋喃致癌活性的有毒代谢产物。为了表征这种不饱和二醛使蛋白质烷基化的化学反应过程，研究了顺式-2-丁烯-1,4-二醛与pH 7.4缓冲液中的模型亲核试剂反应所形成的产物。N(α)-乙酰-L-赖氨酸（AcLys）与顺式-2-丁烯-1,4-二醛反应形成N-取代的吡咯啉-2-酮加合物。N-乙酰-L-半胱氨酸（AcCys）与顺式-2-丁烯-1,4-二醛迅速反应形成多种未鉴定的产物。在该反应混合物中加入AcLys会产生一种连接两个氨基酸残基的N-取代的3-(S-乙酰半胱氨酰)吡咯加合物。当顺式-2-丁烯-1,4-二醛与谷胱甘肽（GSH）混合时，会分离出相关化合物。在这种情况下，顺式-2-丁烯-1,4-二醛会交联两个GSH分子，根据GSH的相对浓度形成环状或非环状加合物。在[甘氨酸-2-³H]GSH存在的情况下，将呋喃与大鼠肝脏微粒体一起孵育会导致形成与双谷胱甘肽缀合物的合成标准品共洗脱的放射性峰。这些研究表明，在呋喃微粒体氧化过程中形成的具有反应活性的顺式-2-丁烯-1,4-二醛与氨基酸残基迅速且完全反应，形成吡咯和吡咯啉-2-酮衍生物。因此，这种代谢产物可能是与蛋白质结合的活化呋喃衍生物的候选物。顺式-2-丁烯-1,4-二醛交联氨基酸的容易程度表明，吡咯-硫醇交联可能与呋喃暴露后观察到的毒性有关。
