Hajos A K, Winston G W
Department of Biochemistry, Louisiana State University, Baton Rouge 70803.
Carcinogenesis. 1991 Apr;12(4):697-702. doi: 10.1093/carcin/12.4.697.
Dinitropyrenes (DNP) are potent bacterial mutagens in the Ames test and genotoxins in cultured mammalian cells. Rat liver cytosol contains nitroreductases that are critical in the activation of DNP to the ultimate DNA-binding species. In order to study the nature and inducibility of liver cytosolic enzymes involved in the activation of DNP, cytosolic nitroreductase activities towards three DNP isomers (1,3-, 1.6- and 1,8-DNP) were determined in Aroclor-pretreated and untreated rats. Aroclor-1254 pretreatment resulted in up to 5-fold induction of cytosolic DNP nitroreductase. This induction was reflected in at least a 15-fold increase in cytosolic NAD(P)H-quinone oxidoreductase (NQOR) (E.C. 1.6.99.2) activity. The rates of nitroreduction for the three DNP isomers followed the order 1,6- greater than 1,8- greater than 1,3-DNP in all cases studied. 1,6-DNP nitroreductase coeluted with NQOR activity upon affinity purification. Highly purified NQOR catalyzed the NADH- and NADPH-dependent reduction of each of the three DNP isomers and displayed the same stereospecificity as the cytosolic activity. These results provide evidence that NQOR participates in the cytosolic nitroreduction of DNP and constitutes a major part of the total DNP nitroreductase activity upon induction of NQOR by Aroclor-1254 pretreatment. Thus, the role of NQOR in the metabolism of these mutagens depends significantly upon the degree to which this enzyme is induced.
二硝基芘（DNP）在艾姆斯试验中是强效细菌诱变剂，在培养的哺乳动物细胞中是基因毒素。大鼠肝细胞溶胶含有硝基还原酶，这些酶在将DNP激活为最终的DNA结合物种中起关键作用。为了研究参与DNP激活的肝细胞溶胶酶的性质和诱导性，在经多氯联苯预处理和未处理的大鼠中测定了针对三种DNP异构体（1,3-、1,6-和1,8-DNP）的细胞溶胶硝基还原酶活性。多氯联苯1254预处理导致细胞溶胶DNP硝基还原酶诱导高达5倍。这种诱导反映在细胞溶胶NAD(P)H-醌氧化还原酶（NQOR）（E.C. 1.6.99.2）活性至少增加15倍。在所有研究的情况下，三种DNP异构体的硝基还原速率遵循1,6-＞1,8-＞1,3-DNP的顺序。亲和纯化后，1,6-DNP硝基还原酶与NQOR活性共洗脱。高度纯化的NQOR催化三种DNP异构体中每一种的NADH和NADPH依赖性还原，并表现出与细胞溶胶活性相同的立体特异性。这些结果提供了证据，表明NQOR参与DNP的细胞溶胶硝基还原，并且在多氯联苯1254预处理诱导NQOR后构成总DNP硝基还原酶活性的主要部分。因此，NQOR在这些诱变剂代谢中的作用很大程度上取决于该酶的诱导程度。
