Davies M J, Truscott R J
The Heart Research Institute, 145 Missenden Road Camperdown, Sydney, NSW 2050, Australia.
J Photochem Photobiol B. 2001 Oct;63(1-3):114-25. doi: 10.1016/s1011-1344(01)00208-1.
Proteins comprise approximately 68% of the dry weight of cells and tissues and are therefore potentially major targets for photo-oxidation. Two major types of processes can occur with proteins. The first of these involves direct photo-oxidation arising from the absorption of UV radiation by the protein, or bound chromophore groups, thereby generating excited states (singlet or triplets) or radicals via photo-ionisation. The second major process involves indirect oxidation of the protein via the formation and subsequent reactions of singlet oxygen generated by the transfer of energy to ground state (triplet) molecular oxygen by either protein-bound, or other, chromophores. The basic principles behind these mechanisms of photo-oxidation of amino acids, peptides and proteins and the potential selectivity of damage are discussed. Emphasis is placed primarily on the intermediates that are generated on amino acids and proteins, and the subsequent reactions of these species, and not the identity or chemistry of the sensitizer itself, unless the sensitizing group is itself intrinsic to the protein. A particular system is then discussed--the cataractous lens--where UV photo-oxidation may play a role in the aetiology of the disease, and tryptophan-derived metabolites act as UV filters.
蛋白质约占细胞和组织干重的68%，因此可能是光氧化的主要靶点。蛋白质可发生两种主要类型的过程。第一种涉及蛋白质或结合的发色团吸收紫外线辐射而产生的直接光氧化，从而通过光电离产生激发态（单线态或三线态）或自由基。第二种主要过程涉及通过蛋白质结合的或其他发色团将能量转移到基态（三线态）分子氧而产生单线态氧，随后蛋白质发生间接氧化。本文讨论了氨基酸、肽和蛋白质光氧化机制背后的基本原理以及潜在的损伤选择性。重点主要放在氨基酸和蛋白质上产生的中间体以及这些物质随后的反应上，而不是敏化剂本身的特性或化学性质，除非敏化基团本身是蛋白质固有的。然后讨论了一个特定的系统——白内障晶状体——紫外线光氧化可能在该疾病的病因学中起作用，色氨酸衍生的代谢产物充当紫外线滤光器。
