Silva E, Barrera M
Radiat Environ Biophys. 1985;24(1):57-61. doi: 10.1007/BF01212653.
Native horseradish peroxidase, as well as its reduced and carboxymethylated form, and the apoenzyme, showed resistance to photodynamic action. Sensitivity to this action was detected only in reduced and carboxymethylated apoenzyme, when the photooxidation of its histidine residues was observed. When analyzing the bulk hydrophobic character (Hf) and the accessibility coefficients (Br) in those amino acid residues which can be subjected to photooxidation in horseradish peroxidase, it was found that all of them are situated in hydrophobic zones with low accessibility coefficients. This could justify the high resistance of this enzyme to photodynamic action. The only exception is tryptophan-117, which has low values of Hf and Br, and therefore its resistance to photodynamic action can only be explained in terms of its location and environment. Tryptophan-117 would be situated in a zone of antiparallel beta-structure, according to Chou and Fasman's predictive method for protein conformation.
天然辣根过氧化物酶及其还原和羧甲基化形式以及脱辅基酶对光动力作用具有抗性。仅在还原和羧甲基化的脱辅基酶中检测到对这种作用的敏感性，此时观察到其组氨酸残基的光氧化。在分析辣根过氧化物酶中可进行光氧化的那些氨基酸残基的整体疏水特性（Hf）和可及性系数（Br）时，发现它们都位于可及性系数较低的疏水区域。这可以解释该酶对光动力作用的高抗性。唯一的例外是色氨酸-117，其Hf和Br值较低，因此其对光动力作用的抗性只能根据其位置和环境来解释。根据Chou和Fasman预测蛋白质构象的方法，色氨酸-117位于反平行β-结构区域。
