Spin-state changes in cytochrome P-450cam on binding of specific substrates.
Spin-state changes in cytochrome P-450cam on binding of specific substrates.
复制标题
细胞色素 P-450cam 与特定底物结合时的自旋状态变化。
DOI：
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发表时间：
1970
影响因子：
11.1
通讯作者：
H. Beinert
中科院分区：
文献类型：
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作者：
R. Tsai;C. Yu;I. C. Gunsalus;J. Peisach;W. Blumberg;W. Orme;H. Beinert
在4.2 ~ 80 ° K温度范围内，观察到恶臭假单胞菌可溶性P-450细胞色素的电子顺磁共振信号。如分离的，P-450具有典型的低自旋铁血红素化合物的信号，其中硫作为轴向配体之一（g = 2.45，2.26，1.91（5））。我们还检测到高自旋铁血红素（g = 8，4，1.8）典型的小信号，相当于在低于20 ° K的温度下小于7%的血红素。在用底物（+）-樟脑滴定时，低自旋信号降低，高自旋信号增加，最大代表血红素的约60%。由于至今尚未了解的原因，40%的血红素不能被（+）或（-）-樟脑转化为高自旋。高自旋信号具有菱形特征，其比先前用血红素化合物观察到的任何特征都强（E = 0.33 cm（-1）; D = 3.8 cm（-1）; E/D = 0.087）。我们得出结论，P-450（凸轮）作为孤立的是等于或大于95%的低自旋形式可能具有硫作为轴向配体之一。底物的结合足以取代该配体，以允许从低自旋形式转化为高自旋形式。
The electron paramagnetic resonance signals of the soluble P-450 cytochrome from Pseudomonas putida were observed at temperatures from 4.2 to 80 degrees K. As isolated, P-450 has a signal typical of a low spin ferric-heme compound with sulfur as one of the axial ligands (g = 2.45, 2.26, 1.91(5)). We also detected a minor signal typical of high spin ferric heme (g = 8, 4, 1.8) equivalent to less than 7% of the heme at temperatures below 20 degrees K. On titration with the substrate, (+)-camphor, the low spin signal decreased and the high spin signal increased, maximally representing about 60% of the heme. For reasons not thus far understood, 40% of the heme is not converted to high spin by either (+) or (-)-camphor. The high spin signal has a rhombic character which is stronger than any previously observed with a heme compound (E = 0.33 cm(-1); D = 3.8 cm(-1); E/D = 0.087). We conclude that P-450(cam) as isolated is equal to or more than 95% in a low spin form probably having sulfur as one of the axial ligands. The binding of substrate displaces this ligand sufficiently to allow for conversion from a low to a high spin form.