Dizdaroglu Miral
Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8311, USA.
Mutat Res. 2003 Oct 29;531(1-2):109-26. doi: 10.1016/j.mrfmmm.2003.07.003.
Reactive oxygen-derived species such as free radicals are formed in living cells by normal metabolism and exogenous sources, and cause a variety of types of DNA damage such as base and sugar damage, strand breaks and DNA-protein cross-links. Living organisms possess repair systems that repair DNA damage. Oxidative DNA damage caused by free radicals and other oxidizing agents is mainly repaired by base-excision repair (BER), which involves DNA glycosylases in the first step of the repair process. These enzymes remove modified bases from DNA by hydrolyzing the glycosidic bond between the modified base and the sugar moiety, generating an apurinic/apyrimidinic (AP) site. Some also possess AP lyase activity that subsequently cleaves DNA at AP sites. Many DNA glycosylases have been discovered and isolated, and their reaction mechanisms and substrate specificities have been elucidated. Most of the known products of oxidative damage to DNA are substrates of DNA glycosylases with broad or narrow substrate specificities. Some possess cross-activity and remove both pyrimidine- and purine-derived lesions. Overlapping activities between enzymes also exist. Studies of substrate specificities have been performed using either oligodeoxynucleotides with a single modified base embedded at a specific position or damaged DNA substrates containing a multiplicity of pyrimidine- and purine-derived lesions. This paper reviews the substrate specificities and excision kinetics of DNA glycosylases that have been investigated with the use of gas chromatography/mass spectrometry and DNA substrates with multiple lesions.
诸如自由基等活性氧衍生物种在活细胞中由正常代谢和外源来源形成，并导致多种类型的DNA损伤，如碱基和糖损伤、链断裂以及DNA-蛋白质交联。生物体拥有修复DNA损伤的系统。由自由基和其他氧化剂引起的氧化性DNA损伤主要通过碱基切除修复（BER）进行修复，该修复过程的第一步涉及DNA糖基化酶。这些酶通过水解修饰碱基与糖部分之间的糖苷键从DNA中去除修饰碱基，产生无嘌呤/无嘧啶（AP）位点。有些还具有AP裂解酶活性，随后在AP位点切割DNA。已经发现并分离出许多DNA糖基化酶，并且阐明了它们的反应机制和底物特异性。大多数已知的DNA氧化损伤产物是具有广泛或狭窄底物特异性的DNA糖基化酶的底物。有些具有交叉活性，可去除嘧啶和嘌呤衍生的损伤。酶之间也存在重叠活性。使用在特定位置嵌入单个修饰碱基的寡脱氧核苷酸或含有多种嘧啶和嘌呤衍生损伤的受损DNA底物进行了底物特异性研究。本文综述了使用气相色谱/质谱法和具有多个损伤的DNA底物研究的DNA糖基化酶的底物特异性和切除动力学。
