Gaffney B J, Mavrophilipos D V, Doctor K S
Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218.
Biophys J. 1993 Mar;64(3):773-83. doi: 10.1016/S0006-3495(93)81438-3.
A form of ferric lipoxygenase-1 has been isolated that gives an EPR spectrum that is dominated by a species of intermediate rhombicity (E/D = 0.065). This species is obtained in the presence of a number of buffers of high concentration and in the absence of fatty acid byproducts of the iron oxidation. The species is unstable over a period of one day with respect to symmetry of the iron. The EPR lineshapes of the unstable species are highly sensitive to the anionic composition of the buffer and to the addition of neutral ligands. These results suggest that newly formed ferric lipoxygenase has weak affinity for a number of ligands. Affinity of charged ligands for the iron center may provide a mechanism for charge compensation as the iron center alternates between ferric and ferrous in the catalytic cycle. We use spectral simulation to evaluate quantitatively the interaction of the ferric center with ligands and also show that a transition in the middle Kramers doublet makes a significant contribution to the EPR spectrum of the more rhombic species.
已分离出一种铁脂氧合酶-1形式，其电子顺磁共振（EPR）谱以一种中等菱形度的物种为主（E/D = 0.065）。该物种是在存在多种高浓度缓冲液且不存在铁氧化产生的脂肪酸副产物的情况下获得的。就铁的对称性而言，该物种在一天内不稳定。不稳定物种的EPR线形对缓冲液的阴离子组成和中性配体的添加高度敏感。这些结果表明，新形成的铁脂氧合酶对多种配体具有弱亲和力。带电配体对铁中心的亲和力可能为催化循环中铁中心在三价铁和二价铁之间交替时的电荷补偿提供一种机制。我们使用光谱模拟来定量评估三价铁中心与配体的相互作用，并且还表明中间克莱默斯二重态的跃迁对更菱形物种的EPR谱有显著贡献。
