Kemal C, Louis-Flamberg P, Krupinski-Olsen R, Shorter A L
Smith Kline and French Laboratories, Swedeland, Pennsylvania 19479.
Biochemistry. 1987 Nov 3;26(22):7064-72. doi: 10.1021/bi00396a031.
Nordihydroguaiaretic acid (NDGA), one of the most efficient inhibitors of lipoxygenases, is shown, by electron paramagnetic resonance, circular dichroism, and fluorescence studies, to reduce the catalytically active ferric soybean lipoxygenase 1 (Eox) to the inactive ferrous form (Ered). In decreasing order of reactivity, the following also reduce Eox: catechol greater than hydroquinone greater than 2,6-di-tert-butyl-4-methylphenol greater than esculetin greater than caffeic acid approximately equal to alpha-tocopherol greater than norepinephrine greater than dithiothreitol. The reduction of Eox by NDGA (kappa = 8.1 X 10(6) M-1 S-1, pH 9.0, 25 degrees C) is almost as fast as the Eox-catalyzed conversion of linoleate (LH) to 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoate (LOOH) and the oxidation of Ered by LOOH to give Eox. Thus, NDGA can efficiently inhibit the Eox-catalyzed conversion of LH to LOOH by reducing Eox to the inactive Ered, thereby diminishing the turnover rate. Lipoxygenase catalyzes the oxidation of NDGA by LOOH at a rate that is consistent with the independently determined rate constant for the reduction of Eox by NDGA. All four reducing equivalents from the two catechol groups in NDGA can be utilized in the reduction of Eox, leading to the consumption of 4 mol of LOOH/mol of NDGA initially present. Because the catalytically inactive Ered is oxidized by fatty acid hydroperoxides (e.g., LOOH) to give the active Eox, reducing agents such as NDGA are most effective as lipoxygenase inhibitors at low hydroperoxide concentrations. Our results suggest that in vivo, where lipid hydroperoxides are maintained at low steady-state levels, reduction of lipoxygenase from the ferric to ferrous state may be important in the regulation of lipoxygenase activity and hence leukotriene biosynthesis.
去甲二氢愈创木酸（NDGA）是脂氧合酶最有效的抑制剂之一，通过电子顺磁共振、圆二色性和荧光研究表明，它能将具有催化活性的大豆脂氧合酶1（Eox）的三价铁形式还原为无活性的二价铁形式（Ered）。按反应活性从高到低的顺序，以下物质也能还原Eox：儿茶酚＞对苯二酚＞2,6 -二叔丁基-4 -甲基苯酚＞七叶亭＞咖啡酸≈α-生育酚＞去甲肾上腺素＞二硫苏糖醇。NDGA对Eox的还原作用（κ = 8.1×10⁶ M⁻¹·s⁻¹，pH 9.0，25℃）几乎与Eox催化亚油酸（LH）转化为13(S)-氢过氧-9(Z),11(E)-十八碳二烯酸（LOOH）以及LOOH将Ered氧化为Eox的速度一样快。因此，NDGA通过将Eox还原为无活性的Ered，能有效抑制Eox催化LH转化为LOOH，从而降低周转率。脂氧合酶催化LOOH氧化NDGA的速率与独立测定的NDGA还原Eox的速率常数一致。NDGA中两个儿茶酚基团的所有四个还原当量都可用于还原Eox，最初每摩尔NDGA会消耗4摩尔LOOH。由于催化无活性的Ered会被脂肪酸氢过氧化物（如LOOH）氧化为活性Eox，所以在低氢过氧化物浓度下，像NDGA这样的还原剂作为脂氧合酶抑制剂最为有效。我们的结果表明，在体内脂质氢过氧化物维持在低稳态水平的情况下，将脂氧合酶从三价铁状态还原为二价铁状态可能对脂氧合酶活性的调节以及白三烯生物合成具有重要意义。
