Domigan N M, Charlton T S, Duncan M W, Winterbourn C C, Kettle A J
Free Radical Research Group, Christchurch School of Medicine, New Zealand.
J Biol Chem. 1995 Jul 14;270(28):16542-8. doi: 10.1074/jbc.270.28.16542.
Hypochlorous acid is the major strong oxidant generated by human neutrophils, and it has the potential to cause much of the tissue damage that these inflammatory cells promote. It is produced from hydrogen peroxide and chloride by the heme enzyme myeloperoxidase. To unequivocally establish that hypochlorous acid contributes to inflammation, a stable and unique marker for its reaction with biomolecules needs to be identified. In this investigation we have found that reagent hypochlorous acid reacts with tyrosyl residues in small peptides and converts them to chlorotyrosine. Purified myeloperoxidase in combination with hydrogen peroxide and chloride, as well as stimulated human neutrophils, chlorinated tyrosine in the peptide Gly-Gly-Tyr-Arg. Rather than reacting directly with the aromatic ring of tyrosine, hypochlorous acid initially reacted with an amine group of the peptide to form a chloramine. The chloramine then underwent an intramolecular reaction with the tyrosyl residue to convert it to chlorotyrosine. This indicates that tyrosyl residues in proteins that are close to amine groups will be susceptible to chlorination. Peroxidases are the only enzymes capable of chlorinating an aromatic ring. Furthermore, myeloperoxidase is the only human enzyme that produces hypochlorous acid under physiological conditions. Therefore, chlorotyrosine will be a specific marker for the production of hypochlorous acid in vivo and for the involvement of myeloperoxidase in inflammatory tissue damage.
次氯酸是人类嗜中性粒细胞产生的主要强氧化剂，它有可能造成这些炎症细胞所引发的大部分组织损伤。它由血红素酶髓过氧化物酶利用过氧化氢和氯化物生成。为了明确证实次氯酸会导致炎症，需要鉴定出一种用于其与生物分子反应的稳定且独特的标志物。在本研究中，我们发现试剂次氯酸与小肽中的酪氨酰残基发生反应，并将它们转化为氯酪氨酸。纯化的髓过氧化物酶与过氧化氢和氯化物一起，以及受到刺激的人类嗜中性粒细胞，会使肽Gly-Gly-Tyr-Arg中的酪氨酸氯化。次氯酸并非直接与酪氨酸的芳香环反应，而是首先与肽的一个胺基反应形成氯胺。然后氯胺与酪氨酰残基发生分子内反应，将其转化为氯酪氨酸。这表明靠近胺基的蛋白质中的酪氨酰残基易受氯化作用影响。过氧化物酶是唯一能够使芳香环氯化的酶。此外，髓过氧化物酶是唯一在生理条件下产生次氯酸的人类酶。因此，氯酪氨酸将是体内次氯酸生成以及髓过氧化物酶参与炎症组织损伤的特异性标志物。
