Duker N J, Hart D M
Cancer Res. 1984 Feb;44(2):602-4.
Phage PBS2 DNA, which contains uracil in place of thymine, was used as substrate for purified Bacillus subtilis uracil:DNA glycosylase. Incubation of this DNA with the ultimate carcinogen N-acetoxy-N-2-acetylaminofluorene resulted in the production of N-(deoxyguanosin-8-yl)acetylaminofluorene. A decreased Vmax resulted from the reaction of the glycosylase with this arylamidated substrate. Addition of a 2-fold excess of control PBS2 DNA following initiation of the reaction with the modified substrate showed delayed dissociation of the enzyme from the arylamidated DNA. This shows that the presence of a carcinogen-modified DNA base can reduce the capacity for uracil excision. Therefore, interference with enzymic release of uracil from DNA may be an indirect mechanism of mutagenesis by carcinogen:DNA adducts.
含有尿嘧啶而非胸腺嘧啶的噬菌体PBS2 DNA被用作纯化的枯草芽孢杆菌尿嘧啶：DNA糖基化酶的底物。将该DNA与最终致癌物N-乙酰氧基-N-2-乙酰氨基芴一起孵育，导致产生N-（脱氧鸟苷-8-基）乙酰氨基芴。糖基化酶与这种芳酰胺化底物的反应导致Vmax降低。在用修饰底物启动反应后加入2倍过量的对照PBS2 DNA，显示酶从芳酰胺化DNA的解离延迟。这表明致癌物修饰的DNA碱基的存在可降低尿嘧啶切除能力。因此，干扰尿嘧啶从DNA的酶促释放可能是致癌物：DNA加合物诱变的间接机制。
