Deutsch J C, Kolhouse J F
Division of Gastroenterology, Veterans Affairs Hospital, Denver, CO 80262.
Mutat Res. 1993 Aug;302(4):183-90. doi: 10.1016/0165-7992(93)90102-2.
The relation of ascorbic acid to the ultraviolet light-induced deamination of cytosine (to uracil) and 5-methylcytosine (to thymine) was examined using gas chromatography-mass spectrometry. There was an inverse relation between the uracil content measured in solutions of cytosine after exposure to short wavelength (254 nm) ultraviolet light and the ascorbic acid concentration of the solution indicating inhibition of deamination of cytosine by ascorbic acid. Ascorbic acid also inhibited ultraviolet light-induced deamination of 5-methylcytosine. The ascorbic acid was only partially consumed during the exposure suggesting that protection from deamination was not due entirely to the antioxidant properties of ascorbic acid. Mercaptoethanol did not prevent ultraviolet light-induced deamination of either cytosine or 5-methylcytosine. However, near identical protection from ultraviolet light-induced deamination was provided by 4-aminobenzoic acid and ascorbic acid at equivalent ultraviolet light absorbing concentrations. This observation suggests that ascorbic acid prevents short wavelength ultraviolet light-induced deamination through absorbance of ultraviolet light rather than through antioxidant mechanisms.
使用气相色谱 - 质谱法研究了抗坏血酸与紫外线诱导的胞嘧啶（脱氨生成尿嘧啶）和5 - 甲基胞嘧啶（脱氨生成胸腺嘧啶）脱氨反应之间的关系。在短波长（254 nm）紫外线照射后的胞嘧啶溶液中测得的尿嘧啶含量与溶液中的抗坏血酸浓度呈负相关，表明抗坏血酸可抑制胞嘧啶的脱氨反应。抗坏血酸也抑制紫外线诱导的5 - 甲基胞嘧啶脱氨反应。在照射过程中抗坏血酸仅被部分消耗，这表明防止脱氨并非完全归因于抗坏血酸的抗氧化特性。巯基乙醇不能阻止紫外线诱导的胞嘧啶或5 - 甲基胞嘧啶脱氨反应。然而，在等效的紫外线吸收浓度下，4 - 氨基苯甲酸和抗坏血酸对紫外线诱导的脱氨反应提供了几乎相同的保护作用。这一观察结果表明，抗坏血酸通过吸收紫外线而非通过抗氧化机制来防止短波长紫外线诱导的脱氨反应。
