Kroeger-Koepke M B, Michejda C J
Cancer Res. 1979 May;39(5):1587-91.
The steady state kinetics and isotope effects were examined for demethylation of dimethylnitrosamine and phenylmethylnitrosamine, as well as their deuterated analogs, using the S-9 fraction, the microsomal pellet, and postmicrosomal supernatant from rat livers. The isotope effect (ratio of maximal rates for the deuterated and light substrates) using the S-9 from Long-Evans rat livers was found to be 1.82 for dimethylnitrosamine and 5.38 for phenylmethylnitrosamine. Phenobarbital was shown to induce dimethylnitrosamine demethylase activity in the microsomal pellet of both Long-Evans and Sprague-Dawley rats but to repress this activity in the postmicrosomal supernatant in the Long-Evans rats, while markedly increasing it in the Sprague-Dawley rats. It was also found that there was nitrosamine demethylase activity in the so-called "pH 5 enzymes" and in the supernatant from that preparation. The latter activity shows substantially different characteristics from that found in the other fractions.
利用大鼠肝脏的S-9组分、微粒体沉淀和微粒体后上清液，研究了二甲基亚硝胺和苯甲基亚硝胺及其氘代类似物的去甲基化的稳态动力学和同位素效应。发现使用来自Long-Evans大鼠肝脏的S-9时，二甲基亚硝胺的同位素效应（氘代底物与轻底物的最大速率之比）为1.82，苯甲基亚硝胺为5.38。苯巴比妥被证明可诱导Long-Evans大鼠和Sprague-Dawley大鼠微粒体沉淀中的二甲基亚硝胺去甲基酶活性，但在Long-Evans大鼠的微粒体后上清液中抑制该活性，而在Sprague-Dawley大鼠中则显著增加该活性。还发现所谓的“pH 5酶”及其制备的上清液中存在亚硝胺去甲基酶活性。后者的活性与在其他组分中发现的活性具有显著不同的特征。
