Rosenkranz P, Schmidt H
Z Naturforsch C Biosci. 1976 Nov-Dec;31(11-12):679-82. doi: 10.1515/znc-1976-11-1209.
The photodynamic deactivation of lysozyme in presence of acridine orange is caused by a reaction between singlet oxygen formed via the dye triplet state and the protein. In order to identify the region where the singlet oxygen reacts with the protein we have investigated the kinetics of the deactivation in presence ofthe inhibitor of the enzymatic reaction N-acetylglucosamine (GlcNAc). The overall experimental rate constant becomes slower with increasing saccharide concentrations. As we can exclude experimentally that this kinetical effect is caused in presence of the saccharide by a physical quenching of singlet oxygen or of the dye triplet state it has to be assumed that GlcNAc protects the surrounding of its bindings place at subsite C of the enzymatic center sterically against an attack of singlet oxygen. In this region three tryptophan residues are located, which could be sensitive against singlet oxygen. Surprisingly, however, it has been found that only those species are protected, in which a second saccharide molecule is bound to the protein, probably at subsite E at the enzymatic center, where no sensitive amino acid side chains are located.
在吖啶橙存在的情况下，溶菌酶的光动力失活是由通过染料三重态形成的单线态氧与蛋白质之间的反应引起的。为了确定单线态氧与蛋白质反应的区域，我们研究了在酶促反应抑制剂N - 乙酰葡糖胺（GlcNAc）存在下失活的动力学。随着糖浓度的增加，整体实验速率常数变慢。由于我们可以通过实验排除在糖存在下这种动力学效应是由单线态氧或染料三重态的物理猝灭引起的，所以必须假定GlcNAc在空间上保护其在酶中心亚位点C的结合位点周围免受单线态氧的攻击。在该区域有三个色氨酸残基，它们可能对单线态氧敏感。然而，令人惊讶的是，已发现只有那些第二个糖分子与蛋白质结合的物种受到保护，第二个糖分子可能结合在酶中心的亚位点E，该位点没有敏感的氨基酸侧链。
