Bishop W H, Henke L, Christopher J P, Millar D B
Proc Natl Acad Sci U S A. 1980 Apr;77(4):1980-2. doi: 10.1073/pnas.77.4.1980.
Ultraviolet irradiation of 11S acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) produces a loss of tryptophan fluorescence which is best described as the sum of two separable first-order processes, one much more rapid than the other. In addition, the enzyme undergoes an all-or-none inactivation that is monotonically first order. Simultaneous with activity loss, photoscission takes place and results in a molecular weight drop of 1 x 10(5); this decrease is first order with a rate constant identical to that for enzymatic inactivation. These processes are accompanied by apparent conformational changes, as shown by circular dichroic and difference absorption spectra. The relative photochemical inactivation efficiency of incident light is unity when corrected for the wavelength dependence of fluorescence excitation, which is consistent with an efficient Förster resonance transfer of energy among the aromatic chromophores. The extreme sensitivity of acetylcholinesterase to photodestruction upon photon absorption and the several events that follow it not only suggest that these findings might be a basis for a useful molecular probe of the structure of this enzyme, but also indicate that additional care should be taken when conducting spectroscopic studies in the UV region.
对11S乙酰胆碱酯酶（乙酰胆碱乙酰水解酶，EC 3.1.1.7）进行紫外线照射会导致色氨酸荧光丧失，这一过程最适合描述为两个可分离的一级过程之和，其中一个比另一个快得多。此外，该酶会经历全或无的失活，且该失活过程呈单调一级反应。与活性丧失同时发生的是光裂解，导致分子量下降1×10⁵ ；这种下降是一级反应，其速率常数与酶失活的速率常数相同。这些过程伴随着明显的构象变化，圆二色光谱和差示吸收光谱表明了这一点。当根据荧光激发的波长依赖性进行校正时，入射光的相对光化学失活效率为1，这与芳香发色团之间高效的Förster共振能量转移相一致。乙酰胆碱酯酶对光子吸收后的光破坏极其敏感，以及随之发生的一系列事件，不仅表明这些发现可能是对该酶结构进行有用分子探测的基础，还表明在紫外区域进行光谱研究时应格外小心。
