Resonance Raman spectroscopic evidence for an anionic flavin semiquinone in bovine liver monoamine oxidase.
Resonance Raman spectroscopic evidence for an anionic flavin semiquinone in bovine liver monoamine oxidase.
复制标题
牛肝单胺氧化酶中阴离子黄素半醌的共振拉曼光谱证据。
DOI：
10.1006/abbi.1993.1025
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发表时间：
1993
影响因子：
3.9
通讯作者：
Edmondson,DE
中科院分区：
文献类型：
--
作者：
Yue,KT;Bhattacharyya,AK;Zhelyaskov,VR;Edmondson,DE
从牛肝中分离的黄素蛋白单胺氧化酶B（MAO B）在412 nm处有一个不寻常的附加吸收带，这与它的阴离子黄素半醌形式（F1）和其它典型的（F1）黄素蛋白的吸收相似。酶的变性导致这种异常吸收的消除。分离的MAO B的共振拉曼（RR）光谱实际上与其连二亚硫酸盐还原（FI）形式的相同。这两个光谱都显示出与黑曲霉葡萄糖氧化酶（GO）的（Fl）形式在300和1700 cm− 1之间的区域内（406.7 nm激发）的RR光谱相似的特征。这些特征容易与氧化黄素、中性黄素半醌和血红素蛋白的特征区分开，强烈表明分离的MAO B中存在（Fl β）形式，即使是在没有光的情况下分离的制剂。MAO B的（F1）型与GO的RR谱或已发表的具有过量底物类似物的D氨基酸氧化酶的（F1）型的RR谱之间存在显著差异。这些差异中的至少一部分可以归因于三种酶中黄素的不同结合。在分离的MAO B中没有观察到由于（Fl-β）引起的EPR信号。连二亚硫酸盐还原的（Flavin）形式表现出比从吸收光谱预期的EPR信号少50%的EPR信号，这表明（Flavin）flavin与蛋白质中未知身份的顺磁中心的可能偶联。这些意见的影响，对MAO B与目前的观点，其催化机制进行了讨论。
The flavoprotein monoamine oxidase B (MAO B) from bovine liver, as isolated, has an unusual additional absorption band at 412 nm, which is similar to the absorption of its anionic flavin semiquinone form, (Fl∸), and other typical (Fl∸) flavoproteins. Denatu ration of the enzyme results in the elimination of this anomalous absorption. The resonance Raman (RR) spectrum of MAO B as isolated is virtually identical to that of its dithionitereduced (Fl∸) form. Both spectra show features similar to those of the RR spectrum of the (Fl∸) form ofAspergillus nigerglucose oxidase (GO) in the region between 300 and 1700 cm−1with 406.7 nm excitation. These features are readily distinguishable from those of oxidized flavin, neutral fiavin semiquinone, and hemoprotein, strongly suggesting the presence of an (Fl∸) form in MAO B as isolated, even with preparations isolated in the absence of light. There are significant differences between the RR spectra of the (Fl∸) form of MAO B and those of GO or the published RR spectra of the (Fl∸) form of Damino acid oxidase with excess substrate analog. At least some of these differences can be attributed to the different binding of flavin in the three enzymes. No EPR signals due to (Fl∸) are observed in MAO B as isolated. The dithionite-reduced (Fl∸) form exhibits 50% less EPR signal than that expected from the absorption spectrum, which suggests a possible coupling of the (Fl∸) fiavin with a paramagnetic center of unknown identity in the protein. The implications of these observations on MAO B with the current view of its catalytic mechanism are discussed.