Anlezark G M, Melton R G, Sherwood R F, Coles B, Friedlos F, Knox R J
Division of Biotechnology, PHLS Centre for Applied Microbiology and Research, Salisbury, Wiltshire, U.K.
Biochem Pharmacol. 1992 Dec 15;44(12):2289-95. doi: 10.1016/0006-2952(92)90671-5.
A nitroreductase enzyme has been isolated from Escherichia coli B. This enzyme is an FMN-containing flavoprotein with a molecular mass of 24 kDa and requires either NADH or NADPH as a cofactor. Partial protein sequence analysis showed extensive homology with the "classical nitroreductase" of Salmonella typhimurium and a nitroreductase induced in Enterobacter cloacae. In common with the Salmonella enzyme, the E. coli B enzyme is capable of reducing nitrofurazone. The E. coli nitroreductase is also capable of reducing the anti-tumour agent CB1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide], a property shared with the mammalian enzyme DT diaphorase [NAD(P)H dehydrogenase (quinone)] as isolated from Walker cells. The reduction of CB1954 by the E. coli enzyme results in the generation of cytotoxic species. Both enzymes also share the properties of being able to reduce quinones and are both inhibited by dicoumarol. The nitroreductase is a more active enzyme against CB1954 (kcat = 360 min-1) than Walker DT diaphorase (kcat = 4 min-1) and also has a lower Km for NADH (6 vs 75 microM).
已从大肠杆菌B中分离出一种硝基还原酶。这种酶是一种含黄素单核苷酸的黄素蛋白，分子量为24 kDa，需要NADH或NADPH作为辅因子。部分蛋白质序列分析表明，它与鼠伤寒沙门氏菌的“经典硝基还原酶”以及阴沟肠杆菌中诱导产生的一种硝基还原酶具有广泛的同源性。与沙门氏菌的酶一样，大肠杆菌B的这种酶能够还原呋喃西林。大肠杆菌的硝基还原酶还能够还原抗肿瘤药物CB1954 [5-(氮丙啶-1-基)-2,4-二硝基苯甲酰胺]，这一特性与从沃克细胞中分离出的哺乳动物酶DT黄递酶[NAD(P)H脱氢酶(醌)]相同。大肠杆菌的这种酶对CB1954的还原作用会产生细胞毒性物质。这两种酶还都具有能够还原醌的特性，并且都受到双香豆素的抑制。这种硝基还原酶对CB1954的活性（催化常数kcat = 360 min-1）比沃克DT黄递酶（kcat = 4 min-1）更高，并且对NADH的米氏常数（Km）也更低（分别为6 μM和75 μM）。
