Photolysis of adenosylcobalamin and radical pair recombination in ethanolamine ammonia-lyase probed on the micro- to millisecond time scale by using time-resolved optical absorption spectroscopy.
Photolysis of adenosylcobalamin and radical pair recombination in ethanolamine ammonia-lyase probed on the micro- to millisecond time scale by using time-resolved optical absorption spectroscopy.
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使用时间分辨光学吸收光谱在微秒到毫秒的时间尺度上探测腺苷钴胺素的光解和乙醇胺解氨酶中的自由基对重组。
DOI：
10.1021/bi801659e
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发表时间：
2009
期刊：
影响因子：
2.9
通讯作者：
Warncke,Kurt
中科院分区：
文献类型：
--
作者：
Robertson,WesleyD;Warncke,Kurt
利用瞬态紫外-可见吸收光谱技术，在10 - 7 - 10 - 1 s时间尺度上，研究了295 K时鼠伤寒沙门氏菌依赖腺苷钴胺素（腺苷钴胺素;辅酶B12）的乙醇胺氨裂解酶（EAL）中腺苷钴胺素（腺苷钴胺素;辅酶B12）的脉冲激光光解生成辅酶（II）丙氨酸的量子产率和衰变动力学。目的是探索Cob（II）alamin−5′-deoxyadenosyl自由基对的形成和稳定机制，这是EAL催化的关键中间体，以及底物结合对此过程的影响。在天然系统中，钴碳键断裂需要底物结合。在EAL中光解的β-Cbl在10−7s时的量子产率为0.08 ± 0.01，比β-Cbl在水溶液中的量子产率（0.23 ± 0.01）小3倍。因此，蛋白质结合位点抑制光产物自由基对的形成。三种光产物状态，Pf，Ps和Pc，确定在全息EAL由不同的钴（II）维生素衰减动力学（下标表示快，慢，和常数，分别）。这些态的一阶衰减速率常数和量子产额如下：Pf为2.2 × 103 s-1和0.02，Ps为4.2 × 102 s-1和0.01，振幅恒定，没有复合，Pc为0.05。底物类似物（S）-1-氨基-2-丙醇与EAL的结合消除了Pfstate，并相对于Ps（0.01）降低了Pc（0.03）的量子产率，但相对于holo-EAL的量子产率或衰减速率常数，没有显著改变Ps的量子产率或衰减速率常数。因此，底物类似物通过改变成对的cob（II）alamin−5′-deoxyadenosyl自由基对状态的笼逃逸速率来影响10− 7 s时的量子产率。然而，没有观察到预测的底物类似物结合诱导的量子产率增加。有人提出，底物类似物不会诱导蛋白质中的自由基对稳定的变化，这是真正的底物的特征。
The quantum yield and kinetics of decay of cob(II)alamin formed by pulsed-laser photolysis of adenosylcobalamin (AdoCbl; coenzyme B12) in AdoCbl-dependent ethanolamine ammonia-lyase (EAL) fromSalmonella typhimuriumhave been studied on the 10−7−10−1s time scale at 295 K by using transient ultraviolet−visible absorption spectroscopy. The aim is to probe the mechanism of formation and stabilization of the cob(II)alamin−5′-deoxyadenosyl radical pair, which is a key intermediate in EAL catalysis, and the influence of substrate binding on this process. Substrate binding is required for cobalt−carbon bond cleavage in the native system. Photolysis of AdoCbl in EAL leads to a quantum yield at 10−7s for cob(II)alamin of 0.08 ± 0.01, which is 3-fold smaller than for AdoCbl in aqueous solution (0.23 ± 0.01). The protein binding site therefore suppresses photoproduct radical pair formation. Three photoproduct states, Pf, Ps, and Pc, are identified in holo-EAL by the different cob(II)alamin decay kinetics (subscripts denote fast, slow, and constant, respectively). These states have the following first-order decay rate constants and quantum yields: 2.2 × 103s−1and 0.02 for Pf, 4.2 × 102s−1and 0.01 for Ps, and constant amplitude, with no recombination, and 0.05 for Pc, respectively. Binding of the substrate analogue (S)-1-amino-2-propanol to EAL eliminates the Pfstate and lowers the quantum yield of Pc(0.03) relative to that of Ps(0.01) but does not significantly change the quantum yield or decay rate constant of Ps, relative to those of holo-EAL. The substrate analogue thus influences the quantum yield at 10−7s by changing the cage escape rate from the geminate cob(II)alamin−5′-deoxyadenosyl radical pair state. However, the predicted substrate analogue binding-induced increase in the quantum yield is not observed. It is proposed that the substrate analogue does not induce the radical pair stabilizing changes in the protein that are characteristic of true substrates.
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影响因子：
2.9
作者：
Marsh, ENG;Ballou, DP
通讯作者：
Ballou, DP
编码鼠伤寒沙门氏菌腺苷钴胺素依赖性乙醇胺解氨酶的基因的克隆、测序和表达。
DOI：
--
发表时间：
1990
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Faust,LR;Connor,JA;Roof,DM;Hoch,JA;Babior,BM
通讯作者：
Babior,BM
B12 辅酶的时间分辨光谱研究：甲钴胺的光解作用与波长相关
影响因子：
3.3
作者：
J. Shiang;L. Walker;N. Anderson;and R G Cole;R. Sension
通讯作者：
R. Sension
维生素 B12 和相关 cob(III) 胺胺的超快激发态动力学。
DOI：
10.1021/ja054374
发表时间：
2006
期刊：
Journal of the American Chemical Society.
影响因子：
--
作者：
Shiang,JosephJ;Cole,AllwynG;Sension,RoseanneJ;Hang,Kun;Weng,Yuxiang;Trommel,JennaS;Marzilli,LuigiG;Lian,Tianquan
通讯作者：
Lian,Tianquan
辅酶 B12 的纳秒瞬态吸收光谱。
DOI：
--
发表时间：
1990
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Chen,E;Chance,MR
通讯作者：
Chance,MR