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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >UNEXPECTED GENETIC AND STRUCTURAL RELATIONSHIPS OF A LONG-FORGOTTEN FLAVOENZYME TO NAD(P)H-QUINONE REDUCTASE (DT-DIAPHORASE)
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UNEXPECTED GENETIC AND STRUCTURAL RELATIONSHIPS OF A LONG-FORGOTTEN FLAVOENZYME TO NAD(P)H-QUINONE REDUCTASE (DT-DIAPHORASE)

机译：长分支黄酮酶与NAD（P）H-醌还原酶（DT-二苯甲醚）的意外遗传和结构关系

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0A mammalian cytosolic FAD-dependent enzyme that catalyzes the reduction of quinones by N-ribosyl- and N-alkyldihydronicotinamides, but not by NADH, NADPH, or NMNH (reduced nicotinamide mononucleotide), was isolated from bovine kidney more than 30 years ago [S. Liao, J. T. Dulaney and H. G. Williams-Ashman (1962) J. Biol. Chem. 237, 2981-2987]. This enzyme is designated here as quinone reduc tase type 2 (QR(2)). Bovine QR2 is a homodimer that migrates on SDS/PAGE at 22 kDa. Three tryptic peptides of bovine QR(2) (representing 39 amino acids) showed 43% identity to human NAD (P) H:quinone reductase (DT-diaphorase; EC 1.6.99.2), here designated QR(1) and 82% identity to a related human cDNA clone [called hNQO(2) by A. K. Jaiswal, P. Burnett, M. Adesnik and O. W. McBride (1990) Biochemistry 29, 1899-1906], and designated here as hQR(2). The protein encoded by the latter cDNA did not show QR activity when tested with conventional nicotinamide nucleotides. The unexpected high homology between the old flavoenzyme and hQR(2) prompted us to clone and overexpress hQR(2). The properties of hQR(2) were identical to those of the flavoenzyme described by S. Liao and H. G. Williams-Ashman, thus establishing their genetic identity. Recombinant human QR(2): (i) reacts with N-ribosyl- and N-alkyldihydronicotinamides, but not with NADH, NADPH, or NMNH; (ii) is very weakly inhibited by dicumarol or Cibacron blue; (iii) is very potently inhibited by benzo[a]pyrene, The x-ray crystal structure of rat QR(1) shows that the 33 amino acid C-terminal tail of QR(1) provides the binding site for the hydrophilic portions of NADH and NADPH. In the absence of this binding site in QR(2), the enzyme retains the essential catalytic machinery, including affinity for FAD, but cannot bind phosphorylated hydride donors. [References: 32]
机译：0 30年前，从牛肾中分离出一种哺乳动物的胞质FAD依赖性酶，该酶催化N-核糖基和N-烷基二氢羟丁二酸而不是NADH，NADPH或NMNH（还原的烟酰胺单核苷酸）还原醌。 。 Liao，J.T. Dulaney和H.G. Williams-Ashman（1962）J.Biol。化学237，2981-2987]。这种酶在这里称为2型醌还原酶（QR（2））。牛QR2是同型二聚体，在22 kDa的SDS / PAGE上迁移。牛QR（2）的三种胰蛋白酶肽（代表39个氨基酸）与人NAD（P）H：醌还原酶（DT-diaphorase; EC 1.6.99.2）的同一性为43％，在此称为QR（1），同一性为82％相关人cDNA克隆[由AK Jaiswal，P.Burnett，M.Adesnik和OW McBride（1990）Biochemistry 29，1899-1906称为hNQO（2）]，在此指定为hQR（2）。当用常规烟酰胺核苷酸测试时，由后一个cDNA编码的蛋白质没有显示QR活性。旧的黄素酶和hQR（2）之间出乎意料的高度同源性促使我们克隆并过表达hQR（2）。 hQR（2）的属性与S. Liao和H. G. Williams-Ashman所描述的黄素酶的属性相同，因此建立了它们的遗传同一性。重组人QR（2）：（i）与N-核糖基和N-烷基二氢烟碱酰胺反应，但不与NADH，NADPH或NMNH反应； （ii）地高美醇或西巴龙蓝的抑制作用非常弱； （iii）对苯并[a] py有很强的抑制作用，大鼠QR（1）的X射线晶体结构表明QR（1）的33个氨基酸的C末端尾巴为苯并[a] py的亲水部分提供了结合位点NADH和NADPH。在QR（2）中没有此结合位点的情况下，该酶保留了必要的催化机制，包括对FAD的亲和力，但无法结合磷酸化的氢化物供体。 [参考：32]

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