Studies on the chlorinating activity of myeloperoxidase.
Studies on the chlorinating activity of myeloperoxidase.
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DOI：
10.1016/s0021-9258(17)33749-3
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发表时间：
1976-03
期刊：
影响因子：
--
通讯作者：
J. E. Harrison;J. Schultz
中科院分区：
文献类型：
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作者：
J. E. Harrison;J. Schultz
利用两种方法证明氯离子通过髓过氧化物酶过氧化成游离物质（HOCl或Cl 2）。过氧化物酶引起放射性从含有过氧化氢和[36 Cl]NaCl的溶液中挥发，并且当含有这些组分的溶液通过吸附有过氧化物酶的Millipore过滤器时催化HOCl的形成。在该流动系统中，90 μ g犬髓过氧化物酶在200 μ M H2 O2存在下以对应于100 min-1的周转率产生80 μ M HOCl。在这些条件下，邻甲苯胺，其氧化可以耦合到Cl-过氧化在自由溶液中，没有加速营业额。与氯过氧化物酶和辣根过氧化物酶相反，髓过氧化物酶不利用氯进行氯化反应。这种氧化剂使酶失活。在低pH下，氯离子抑制过氧化氢和次氯酸盐对髓过氧化物酶的氧化（生成稳定的化合物II）。因此，受体氯化不是髓过氧化物酶机制中的速率控制反应，并且在氯化条件下，功能性过氧化物酶对的电位高于HOCl/Cl-对。产物形成步骤可以是以HOCl为代价的化合物I形成的逆过程，而不是通过氯过氧化物酶样氯化中间体氯化Cl-。
Two methods were utilized to demonstrate the peroxidation of chloride ion to a free species (HOCl or Cl2) by myeloperoxidase. The peroxidase caused the volatilization of radioactivity from soultions containing hydrogen peroxide and [36Cl]NaCl, and catalyzed the formation of HOCl when solutions contianing these components were passed through a Millipore filter to which the peroxidase was adsorbed. In this flow system, 90 mug of canine myeloperoxidase generated 80 muM HOCl in the presence of 200 muM H2O2 at a rate corresponding to a turnover of 100 min-1. Under these conditions, o-tolidine, whose oxidation can be coupled to Cl- peroxidation in free solution, did not accelerate turnover. In contrast to chloroperoxidase and horseradish peroxidase, myeloperoxidase does not utilize chlorite for chlorination reactions. This oxidant inactivates the enzyme. At low pH, chloride ion suppresses the oxidation of myeloperoxidase (to the stable compound II) by both hydrogen peroxide and hypochlorite. Acceptor chlorination is therefore not a rate-controlling reaction in the myeloperoxidase mechanism, and the potential of the functional peroxidase couple is higher than the HOCl/Cl- couple under chlorinating conditions. The product-forming step may be a reverse of compound I formation at the expense of HOCl, rather than the chlorination of Cl- by a chloroperoxidase-like chlorinating intermediate.