Papp S, King T E, Vanderkooi J M
Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia 19104.
FEBS Lett. 1991 May 20;283(1):113-6. doi: 10.1016/0014-5793(91)80566-l.
Cytochrome oxidase exhibits phosphorescence from tryptophan in aqueous solution in the absence of oxygen. The lifetime for the resting reduced enzyme suspended in Tween-20 is around 30 ms at pH 8. The lifetime is longest between pH 7 and 8 and decreases with lowering of pH. Oxygen quenches the phosphorescence with a Stern-Volmer quenching constant of approximately 5 x 10(7) M-1.s-1 at 5 degrees C whereas cytochrome c has no effect. We interpret these results to indicate that room temperature tryptophan phosphorescence arises from tryptophan(s) in structured region(s) remote from the hemes and that the protein does not impose a significant barrier for the diffusion of oxygen.
在无氧条件下，细胞色素氧化酶在水溶液中会发出色氨酸的磷光。悬浮于吐温 - 20中的静止还原态酶在pH值为8时的寿命约为30毫秒。该寿命在pH值7至8之间最长，并随着pH值降低而缩短。在5摄氏度时，氧气对磷光的猝灭符合斯特恩 - 沃尔默猝灭常数，约为5×10⁷ M⁻¹·s⁻¹，而细胞色素c则无影响。我们对这些结果的解释是，室温下色氨酸磷光来自远离血红素的结构化区域中的色氨酸，并且蛋白质对氧气扩散没有显著阻碍。
