Resonance Raman evidence for tyrosine involvement in the radical site of galactose oxidase.
Resonance Raman evidence for tyrosine involvement in the radical site of galactose oxidase.
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DOI：
10.1016/s0021-9258(18)83205-7
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发表时间：
1989-05
期刊：
影响因子：
--
通讯作者：
M. Whittaker;V. L. Devito;S. Asher;J. W. Whittaker
中科院分区：
文献类型：
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作者：
M. Whittaker;V. L. Devito;S. Asher;J. W. Whittaker
共振拉曼数据报告的氧化还原活化形式的半乳糖氧化酶从Dactyelodendroides。红色（659 nm）和蓝色（457.9 nm）吸收带内的激发导致在550、1170、1247、1484和1595 cm−1处连接的酪氨酸振动模式的强烈共振增强。环模频率异常低，表明环中键级降低。这些光谱在频率和相对强度上都明显不同于已知芳香族π-自由基的特征光谱。增强酪氨酸环模式的激发吸收带内先前与活性位点中的自由基的存在下，表明连接的酪氨酸残基是存在于自由基的网站，并可能通过形成一个电荷转移复合物稳定这种自由基物种。在半乳糖氧化酶的N3−加合物中观察到一个显著不同的拉曼光谱，显示出一个单一的强1483 cm− 1特征。半乳糖氧化酶的强可见-近红外吸收带可能来自芳香族自由基和酪氨酸-铜络合物之间的电荷转移络合物内的跃迁。
Resonance Raman data are reported for the redox-activated form of galactose oxidase fromDactylium dendroides. Excitation within the red (659 nm) and blue (457.9 nm) absorption bands leads to strong resonance enhancement of ligated tyrosine vibrational modes at 550, 1170, 1247, 1484, and 1595 cm−1. The ring mode frequencies are unusually low, indicating a decreased bond order in the ring. The spectra clearly differ in both frequencies and relative intensities from those characteristic of known aromatic π-radicals. Enhancement of tyrosine ring modes on excitation within absorption bands previously associated with the presence of the radical in the active site suggests that the ligated tyrosine residue is present in the radical site and may stabilize this radical species through formation of a charge transfer complex. A dramatically different Raman spectrum is observed for the N3−adduct of galactose oxidase, exhibiting a single strong 1483 cm−1feature. The intense visible-near IR absorption bands for galactose oxidase may derive from transitions within a charge transfer complex between an aromatic free radical and a tyrosine-copper complex.