Studies of the oxygen binding site of cytochrome P-450. Nitric oxide as a spin-label probe.
Studies of the oxygen binding site of cytochrome P-450. Nitric oxide as a spin-label probe.
复制标题
细胞色素 P-450 氧结合位点的研究。
DOI：
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发表时间：
1978
影响因子：
4.8
通讯作者：
J. Peterson
中科院分区：
文献类型：
--
作者：
D. O'Keeffe;R. Ebel;J. Peterson
恶臭假单胞菌和大鼠肝微粒体细胞色素P-450形成两个铁。和亚铁没有络合物铁-NO络合物是稳定的，在5-300 K温度范围内没有ESR谱，这表明NO的未成对电子与血红素铁的单个未成对d电子是自旋配对的。细菌细胞色素的亚铁.NO复合物是相当稳定的;然而，微粒体酶的相当复合物的一部分迅速变性为五配位的P-420.NO种类。微粒体酶的亚铁.NO复合物变成五配位的百分比似乎取决于原始铁酶中存在的高自旋细胞色素的量，因为它在外源性I型底物的存在下较少。此外，基板，d-樟脑，细菌细胞色素P-450不影响的光吸收或电子自旋共振（ESR）光谱的铁。或亚铁没有络合物铁肝微粒体细胞色素P-450的光吸收差光谱取决于高（底物结合）铁低自旋（无底物）状态的酶的百分比。三价铁的Soret吸收带最大值。这些细胞色素P450的NO复合物比辣根过氧化物酶的相应复合物向更长的波长移动。细胞色素P-450的亚铁-NO复合物的ESR谱显示了在g信号中具有三重超精细相互作用的菱形对称性。与辣根过氧化物酶不同，g没有九线超精细结构，
Pseudomonas putida and rat liver microsomal cytochromes P-450 form both ferric. and ferrous.NO complexes. The ferric.NO complexes are stable and do not possess ESR spectra in the temperature range 5-300 K which suggests that the unpaired electron of the bound NO is spin-paired with the single unpaired d electron of the hemin iron. The ferrous.NO complex of the bacterial cytochrome is quite stable; however, a portion of the comparable complex of the microsomal enzyme rapidly denatures to a five-coordinate P-420.NO species. The percentage of the ferrous.NO complex of the microsomal enzyme which becomes five-coordinate appears to be dependent upon the amount of high spin cytochrome present in the original ferric enzyme since it is less in the presence of exogenous Type I substrates. The addition of the substrate, d-camphor, to the bacterial cytochrome P-450 does not affect the optical absorbance or electron spin resonance (ESR) spectra of either the ferric. or ferrous.NO complexes. The optical absorbance difference spectrum of the ferricNO uersus ferric liver microsomal cytochrome P-450 is dependent upon the percentage of the enzyme in the high (substrate-bound) uersus low spin (substrate-free) state. The Soret absorbance band maxima of the ferric. and ferrous.NO complexes of these cytochromes P450 are shifted to longer wavelengths than those of the corresponding complexes of horseradish peroxidase. The ESR spectra of the ferrous.NO complexes of cytochromes P-450 reveal rhombic symmetry with a triplet hyperfine interaction in the g, signal. Unlike horseradish peroxidase, there is no nine-line superhyperfine structure for the g,