Park M, Loeppky R N
Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA.
Chem Res Toxicol. 2000 Feb;13(2):72-81. doi: 10.1021/tx990126d.
The deamination of DNA bases by three alpha-nitrosaminoaldehydes, butylethanalnitrosamine, methylethanalnitrosamine, and N-nitroso-2-hydroxymorpholine (NHMOR), the direct metabolite of potent animal carcinogen N-nitrosodiethanolamine, was demonstrated by a set of in vitro experiments. The deamination of guanine, adenine, and cytosine bases in nucleotides, oligonucleotides, and calf thymus DNA gave xanthine, hypoxanthine, and uracil, respectively. The order of relative reactivities of the bases was as listed above. Deamination of cytosine to uracil was detected by the reaction of (32)P-labeled oligonucleotide ([5'-(32)P]CGAT) followed by enzymatic hydrolysis. Quantitative analysis of deamination of guanine and adenine in calf thymus DNA was performed by a gas chromatography/mass spectrometry-selected ion monitoring method. Both the extent and the rate of the deamination reactions which occur by transnitrosation from the alpha-nitrosaminoaldehyde to the base were determined for formation of xanthine and hypoxanthine. The deamination of guanine by NHMOR remained significant at low substrate levels.
通过一组体外实验证明了三种α-亚硝基氨基醛（丁基乙基亚硝胺、甲基乙基亚硝胺和N-亚硝基-2-羟基吗啉（NHMOR），强效动物致癌物N-亚硝基二乙醇胺的直接代谢产物）对DNA碱基的脱氨作用。核苷酸、寡核苷酸和小牛胸腺DNA中的鸟嘌呤、腺嘌呤和胞嘧啶碱基脱氨分别生成黄嘌呤、次黄嘌呤和尿嘧啶。碱基的相对反应活性顺序如上所列。通过(32)P标记的寡核苷酸（[5'-(32)P]CGAT）反应后进行酶水解来检测胞嘧啶脱氨生成尿嘧啶。采用气相色谱/质谱选择离子监测法对小牛胸腺DNA中鸟嘌呤和腺嘌呤的脱氨进行定量分析。测定了从α-亚硝基氨基醛向碱基进行亚硝基转移反应生成黄嘌呤和次黄嘌呤的脱氨反应程度和速率。在低底物水平下，NHMOR对鸟嘌呤的脱氨作用仍然显著。
