Siddiqui M A, Fujiwara S, Imanaka T
Department of Biotechnology, Graduate School of Engineering, Osaka University, Japan.
Mol Gen Genet. 1997 Apr 28;254(4):433-9. doi: 10.1007/pl00008607.
Indolepyruvate ferredoxin oxidoreductase (IOR) catalyzes the oxidative decarboxylation of arylpyruvates. Gene cloning and sequencing analysis of the IOR gene from the hyperthermophilic archaeon Pyrococcus sp. KOD1 was performed. Two genes, iorA and iorB. encoding alpha and beta subunits of IOR were found to be tandemly arranged, which suggests that gene expression is translationally coupled. Sequence analysis showed the C-terminal region of the alpha subunit to have a typical ferredoxin-type [4Fe-4S] cluster motif (CXXCXXCXXCXXXCP), which is similar to that present in the delta subunits of other oxidoreductases such as pyruvate ferredoxin oxidoreductase (POR) and 2-ketoisovalerate ferredoxin oxidoreductase (VOR). We suggest that the alpha subunit of KOD1-IOR has a mosaic structure composed of features characteristic of the alpha, beta and delta subunits from POR and VOR. KOD1-IOR was overproduced in anaerobically incubated Escherichia coli cells and the crude enzyme was extracted under anaerobic conditions. The optimal temperature for activity of recombinant IOR was 70 degrees C and the half-life of this enzyme in the presence of air was 15 min at 25 degrees C.
吲哚丙酮酸铁氧化还原酶（IOR）催化芳基丙酮酸的氧化脱羧反应。对嗜热古菌火球菌属KOD1菌株的IOR基因进行了基因克隆和序列分析。发现编码IOR的α和β亚基的两个基因iorA和iorB串联排列，这表明基因表达是翻译偶联的。序列分析表明，α亚基的C末端区域具有典型的铁氧化还原蛋白型[4Fe-4S]簇基序（CXXCXXCXXCXXXCP），这与其他氧化还原酶如丙酮酸铁氧化还原酶（POR）和2-酮异戊酸铁氧化还原酶（VOR）的δ亚基中的基序相似。我们认为，KOD1-IOR的α亚基具有由POR和VOR的α、β和δ亚基的特征组成的嵌合结构。在厌氧培养的大肠杆菌细胞中过量表达KOD1-IOR，并在厌氧条件下提取粗酶。重组IOR的最佳活性温度为70℃，该酶在空气中25℃下的半衰期为15分钟。
