Palumbo A, d'Ischia M, Misuraca G, De Martino L, Prota G
Zoological Station, Naples, Italy.
Biochim Biophys Acta. 1995 Oct 19;1245(2):255-61. doi: 10.1016/0304-4165(95)00094-r.
The mechanism of formation of 5-S-cysteinyldopamine (5-S-CDA), a putative index of oxidative stress in dopaminergic regions of the brain, was investigated by comparing the ability of a number of neurochemically relevant oxidising systems to promote the conjugation of dopamine with cysteine in vitro. Autoxidation of the catecholamine proceeds at relatively slow rate in the physiological pH range, and is little affected by 1 mM Fe(2+)-EDTA complex. In the presence of cysteine, however, the Fe(2+)-induced autoxidation is hastened, affording little amounts of 5-S-CDA. Formation of the adduct is completely suppressed by ascorbic acid. Hydrogen peroxide, in the presence of Fe(2+)-EDTA (Fenton-type oxidation) or peroxidase, promotes a relatively efficient conversion of dopamine to 5-S-CDA and the minor isomer 2-S-CDA. Noteworthy, 15-hydroperoxyeicosatetraenoic acid (arachidonic acid hydroperoxide, HPETE), in the presence of Fe(2+)-EDTA complex, can also mediate 5-S-CDA formation, whilst superoxide radicals are little effective. Overall, these results suggest that ferrous ions, hydrogen peroxide and lipoperoxides may play an important role in 5-S-CDA generation.
5-S-半胱氨酰多巴胺（5-S-CDA）被认为是大脑多巴胺能区域氧化应激的一个指标，本文通过比较一些与神经化学相关的氧化系统在体外促进多巴胺与半胱氨酸结合的能力，研究了其形成机制。儿茶酚胺在生理pH范围内的自氧化速率相对较慢，且受1 mM Fe(2+)-EDTA络合物的影响较小。然而，在半胱氨酸存在的情况下，Fe(2+)诱导的自氧化会加速，生成少量的5-S-CDA。抗坏血酸可完全抑制加合物的形成。在Fe(2+)-EDTA（芬顿型氧化）或过氧化物酶存在的情况下，过氧化氢可促进多巴胺相对有效地转化为5-S-CDA和次要异构体2-S-CDA。值得注意的是，在Fe(2+)-EDTA络合物存在的情况下，15-氢过氧化二十碳四烯酸（花生四烯酸氢过氧化物，HPETE）也可介导5-S-CDA的形成，而超氧自由基的作用较小。总体而言，这些结果表明亚铁离子、过氧化氢和脂过氧化物可能在5-S-CDA的生成中起重要作用。
