Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil.
J Am Chem Soc. 2011 Dec 28;133(51):20761-8. doi: 10.1021/ja2051414. Epub 2011 Dec 5.
Diacetyl, methylglyoxal, and glyoxal are α-dicarbonyl catabolites prone to nucleophilic additions of amino groups of proteins and nucleobases, thereby triggering adverse biological responses. Because of their electrophilicity, in aqueous medium, they exist in a phosphate-catalyzed dynamic equilibrium with their hydrate forms. Diacetyl and methylglyoxal can be attacked by peroxynitrite (k(2) ≈ 1.0 × 10(4) M(-1) s(-1) and k(2) ≈ 1.0 × 10(5) M(-1) s(-1), respectively), a potent biological nucleophile and oxidant, yielding the acetyl radical from the homolysis of peroxynitrosocarbonyl adducts, and acetate or formate ions, respectively. We report here that glyoxal also reacts with peroxynitrite, yielding formate ion at rates at least 1 order of magnitude greater than does methylglyoxal. A triplet EPR signal (1:2:1; a(H) = 0.78 mT) attributable to hydrated formyl radical was detected by direct flow experiments. In the presence of the spin trap 2-methyl-2-nitrosopropane, the EPR spectrum displays the di-tert-butyl nitroxide signal, another signal assignable to the spin trapping adduct with hydrogen radical (a(N) = a(H) = 1.44 mT), probably formed from formyl radical decarbonylation, and a third EPR signal assignable to the formyl radical adduct of the spin trap (a(N) = 0.71 mT and a(H) = 0.14 mT). The novelty here is the detection of singlet oxygen ((1)Δ(g)) monomol light emission at 1270 nm during the reaction, probably formed by subsequent dioxygen addition to formyl radical and a Russell reaction of nascent formylperoxyl radicals. Accordingly, the near-infrared emission increases upon raising the peroxynitrite concentration in D(2)O buffer and is suppressed upon addition of O(2) ((1)Δ(g)) quenchers (NaN(3), l-His, H(2)O). Unequivocal evidence of O(2) ((1)Δ(g)) generation was also obtained by chemical trapping of (18)O(2) ((1)Δ(g)) with anthracene-9,10-divinylsulfonate, using HPLC/MS/MS for detection of the corresponding 9,10-endoperoxide derivative. Our studies add insights into the molecular events underlying nitrosative, oxidative, and carbonyl stress in inflammatory processes and aging-associated maladies.
二乙酰、甲基乙二醛和乙二醛是易于与蛋白质和碱基的氨基发生亲核加成的α-二羰基化合物，从而引发不良的生物学反应。由于其亲电性，在水介质中，它们以磷酸盐催化的动态平衡形式存在于其水合物形式中。二乙酰和甲基乙二醛可被过氧亚硝酰（k(2) ≈ 1.0 × 10(4) M(-1) s(-1) 和 k(2) ≈ 1.0 × 10(5) M(-1) s(-1)）攻击，过氧亚硝酰是一种有效的生物亲核试剂和氧化剂，可使过氧硝酰羰基加合物发生均裂，生成乙酰基自由基和乙酸根或甲酸盐离子。我们在此报告，乙二醛也与过氧亚硝酰反应，生成甲酸盐离子的速率比甲基乙二醛至少高 1 个数量级。通过直接流动实验检测到可归因于水合甲酰自由基的三重态 EPR 信号（1:2:1；a(H) = 0.78 mT）。在自旋捕获剂 2-甲基-2-亚硝基丙烷的存在下，EPR 谱显示出二特丁基氮氧化物信号，另一个信号可归因于氢自由基的自旋捕获加合物（a(N) = a(H) = 1.44 mT），可能是由甲酰基自由基脱羰基形成的，还有第三个 EPR 信号可归因于自旋捕获剂的甲酰基自由基加合物（a(N) = 0.71 mT 和 a(H) = 0.14 mT）。这里的新颖之处在于检测到反应过程中单重态氧（(1)Δ(g)）单分子发光，波长为 1270nm，可能是由甲酰基自由基与随后的氧气加成形成的，以及初生甲酰过氧自由基的 Russell 反应。因此，随着 D(2)O 缓冲液中过氧亚硝酰浓度的升高，近红外发射增加，并且在添加 O(2) ((1)Δ(g))猝灭剂（NaN(3)、l-His、H(2)O）时被抑制。通过用蒽-9,10-二乙烯基磺酸盐化学捕获(18)O(2) ((1)Δ(g))，并用 HPLC/MS/MS 检测相应的 9,10-内过氧化物衍生物，也获得了 O(2) ((1)Δ(g))生成的明确证据。我们的研究为炎症过程和与衰老相关的疾病中氮氧化、氧化和羰基应激的分子事件提供了新的见解。
