Institute of Chemical Biology and Fundamental Medicine, Siberian Division of the Russian Academy of Sciences, pr. Lavrentieva 8, Novosibirsk, Russia.
Biochemistry (Mosc). 2009 Nov;74(11):1253-9. doi: 10.1134/s000629790911011x.
Prokaryotic enzymes formamidopyrimidine-DNA glycosylase (Fpg) and endonuclease VIII (Nei) and their eukaryotic homologs NEIL1, NEIL2, and NEIL3 define the Fpg family of DNA glycosylases, which initiate the process of repair of oxidized DNA bases. The repair of oxidative DNA lesions is known to be impaired in vivo in the presence of ions of some heavy metals. We have studied the effect of salts of several alkaline earth and transition metals on the activity of Fpg-family DNA glycosylases in the reaction of excision of 5,6-dihydrouracil, a typical DNA oxidation product. The reaction catalyzed by NEIL1 was characterized by values K(m) = 150 nM and k(cat) = 1.2 min(-1), which were in the range of these constants for excision of other damaged bases by this enzyme. NEIL1 was inhibited by Al3+, Ni2+, Co2+, Cd2+, Cu2+, Zn2+, and Fe2+ in Tris-HCl buffer and by Cd2+, Zn2+, Cu2+, and Fe2+ in potassium phosphate buffer. Fpg and Nei, the prokaryotic homologs of NEIL1, were inhibited by the same metal ions as NEIL1. The values of I(50) for NEIL1 inhibition were 7 microM for Cd2+, 16 microM for Zn2+, and 400 microM for Cu2+. The inhibition of NEIL1 by Cd2+, Zn2+, and Cu2+ was at least partly due to the formation of metal-DNA complexes. In the case of Cd2+ and Cu2+, which preferentially bind to DNA bases rather than phosphates, the presence of metal ions caused the enzyme to lose the ability for preferential binding to damaged DNA. Therefore, the inhibition of NEIL1 activity in removal of oxidative lesions by heavy metal ions may be a reason for their co-mutagenicity under oxidative stress.
原核酶形成嘧啶二聚体 DNA 糖基化酶（Fpg）和内切核酸酶 VIII（Nei）及其真核同源物 NEIL1、NEIL2 和 NEIL3 定义了 Fpg 家族的 DNA 糖基化酶，该酶启动氧化 DNA 碱基修复过程。已知在存在某些重金属离子的情况下，氧化 DNA 损伤的修复会受到体内的损害。我们研究了几种碱土金属和过渡金属盐对 Fpg 家族 DNA 糖基化酶在切除 5,6-二氢尿嘧啶（一种典型的 DNA 氧化产物）反应中活性的影响。NEIL1 催化的反应的特征是 K(m) = 150 nM 和 k(cat) = 1.2 min(-1)，这在该酶切除其他受损碱基的这些常数范围内。在 Tris-HCl 缓冲液中，Al3+、Ni2+、Co2+、Cd2+、Cu2+、Zn2+ 和 Fe2+ 抑制 NEIL1，在 KPO4 缓冲液中，Cd2+、Zn2+、Cu2+ 和 Fe2+ 抑制 NEIL1。Fpg 和 Nei 是 NEIL1 的原核同源物，与 NEIL1 一样被相同的金属离子抑制。NEIL1 抑制的 I(50) 值分别为 Cd2+ 7 μM、Zn2+ 16 μM 和 Cu2+ 400 μM。Cd2+、Zn2+ 和 Cu2+ 对 NEIL1 的抑制至少部分是由于形成了金属-DNA 复合物。在 Cd2+ 和 Cu2+ 的情况下，它们优先与 DNA 碱基而不是磷酸结合，金属离子的存在导致酶失去对受损 DNA 的优先结合能力。因此，重金属离子对氧化损伤的 NEIL1 活性的抑制可能是它们在氧化应激下共致突变性的原因之一。
