The active form of the ferric heme in neutrophil cytochrome b558 is low-spin in the reconstituted cell-free system in the presence of amphophil
The active form of the ferric heme in neutrophil cytochrome b558 is low-spin in the reconstituted cell-free system in the presence of amphophil
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DOI：
10.1093/oxfordjournals.jbchem.a022507
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发表时间：
1999-10-01
影响因子：
2.7
通讯作者：
Johnson, MK
中科院分区：
文献类型：
--
作者：
Fujii, H;Finnegan, MG;Johnson, MK
超氧阴离子（O-2（.-））-在生理条件下，用室温磁圆二色性（MCD）检测了从猪中性粒细胞中纯化的细胞色素B（588）的产生。通过pH调节或热处理制备了具有不同量的Ism-自旋和高自旋血红素的细胞色素B（588），并将O-2（.-）-发现无细胞系统中的形成活性与低自旋血红素含量相关。O-2（.-）的可能性-还研究了由在阴离子两性嗜粒细胞活化期间诱导的瞬时高自旋铁血红素形式产生的形成活性。花生四烯酸或肉豆蔻酸激活的细胞色素B（588）的EPR谱表明，在花生四烯酸存在下，出现了占血红素约50%的瞬时高自旋铁物种，而在肉豆蔻酸存在下则没有。因此，一个短暂的高自旋铁血红素物种的外观激活与一个两性不提供一个共同的激活机制，在NADPH氧化酶系统。花生四烯酸活化细胞色素B（588）的EPR结果表明，瞬时高自旋铁血红素可以结合氰化物。然而，高自旋铁血红素不有助于O-2（.-）在存在氰化物的无细胞试验中细胞色素B（588）的产生。
The spin state of the heme in superoxide (O-2(.-))-producing cytochrome b(588) purified from pig neutrophils was examined by means of room-temperature magnetic circular dichroism (MCD) under physiological conditions. Cytochrome b(588) with varying amounts of Ism-spin and high-spin heme was prepared by either pH adjustment or heat treatment, and the O-2(.-)-forming activity in a cell-free system was found to correlate with the low-spin heme content. The possibility that the O-2(.-)-forming activity results from a transient high-spin ferric heme form that is induced during activation by anionic amphophils has also been investigated. EPR spectra of cytochrome b(588) activated by either arachidonic acid or myristic acid, showed that a transient high-spin ferric species accounting for approximately 50% of the heme appeared in the presence of arachidonic acid, but not in the presence of myristic acid. Hence the appearance of a transient high-spin ferric heme species on activation with an amphophil does not afford a common activation mechanism in the NADPH oxidase system. The EPR results for cytochrome b(588) activated with arachidonic acid showed that the transient high-spin ferric heme can bind cyanide. However, the high-spin ferric heme does not contribute to the O-2(.-) production of cytochrome b(588) in cell-free assays in the presence of cyanide.