Flavodoxin:quinone reductase (FqrB): a redox partner of pyruvate:ferredoxin oxidoreductase that reversibly couples pyruvate oxidation to NADPH production in Helicobacter pylori and Campylobacter jejuni.
Flavodoxin:quinone reductase (FqrB): a redox partner of pyruvate:ferredoxin oxidoreductase that reversibly couples pyruvate oxidation to NADPH production in Helicobacter pylori and Campylobacter jejuni.
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黄素氧还蛋白：醌还原酶 (FqrB)：丙酮酸：铁氧还蛋白氧化还原酶的氧化还原伙伴，可逆地将丙酮酸氧化与幽门螺杆菌和空肠弯曲杆菌中的 NADPH 产生偶联。
DOI：
10.1128/jb.00287-07
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发表时间：
2007
影响因子：
3.2
通讯作者：
Hoffman,PaulS
中科院分区：
文献类型：
--
作者：
StMaurice,Martin;Cremades,Nunilo;Croxen,MatthewA;Sisson,Gary;Sancho,Javier;Hoffman,PaulS
在幽门螺杆菌（Helicobacter pylori）的细胞提取物中发现了丙酮酸依赖的NADP还原反应，但NADP不是纯化的丙酮酸：铁氧还蛋白氧化还原酶（PFOR）的底物，提示有其他氧化还原活性酶介导了这一反应。在这里，我们表明，fqrB（HP 1164），这是必不可少的和高度保守的ε-proteobacteria，表现出NADPH氧化还原酶活性。FqrB在大肠杆菌中过表达后，通过镍相互作用层析纯化。该蛋白含有黄素腺嘌呤二核苷酸，对甲萘醌或苯醌具有NADPH醌还原酶活性，对细胞色素、分子氧和5，5 ′-二硫代-双-2-硝基苯甲酸（DTNB）具有较弱的还原活性。FqrB表现出乒乓催化机制，akcat为122 s−1，甲萘醌的表观Km为14 μM，NADPH的表观Km为26 μM。FqrB还减少了PFOR的电子载体flavodoxin（FldA）。在纯化的PFOR和FldA的偶联酶测定中，FqrB以丙酮酸和还原型辅酶A（CoA）依赖性方式还原NADP。此外，在NADPH、CO2和乙酰辅酶A的存在下，PFOR：FldA：FqrB复合物通过CO2固定产生丙酮酸。PFOR是复合物中的限速酶，而硝唑尼特是PFOR的特异性抑制剂。pylori和空肠弯曲杆菌也抑制无细胞裂解物中NADP的减少。这些嗜二氧化碳（需要CO2）的生物体在中枢代谢途径中含有间隙，这些间隙将从通过CO2固定形成丙酮酸盐中获益。因此，FqrB在丙酮酸代谢中提供了一种新的功能，并且与在高氧张力下通过醌还原产生超氧阴离子一起，有助于定义ε-变形菌群的独特微好氧生活方式。
Pyruvate-dependent reduction of NADP has been demonstrated in cell extracts of the human gastric pathogenHelicobacter pylori.However, NADP is not a substrate of purified pyruvate:ferredoxin oxidoreductase (PFOR), suggesting that other redox active enzymes mediate this reaction. Here we show thatfqrB(HP1164), which is essential and highly conserved among the epsilonproteobacteria, exhibits NADPH oxidoreductase activity. FqrB was purified by nickel interaction chromatography following overexpression inEscherichia coli. The protein contained flavin adenine dinucleotide and exhibited NADPH quinone reductase activity with menadione or benzoquinone and weak activity with cytochromec, molecular oxygen, and 5,5′-dithio-bis-2-nitrobenzoic acid (DTNB). FqrB exhibited a ping-pong catalytic mechanism, akcatof 122 s−1, and an apparentKmof 14 μM for menadione and 26 μM for NADPH. FqrB also reduced flavodoxin (FldA), the electron carrier of PFOR. In coupled enzyme assays with purified PFOR and FldA, FqrB reduced NADP in a pyruvate- and reduced coenzyme A (CoA)-dependent manner. Moreover, in the presence of NADPH, CO2, and acetyl-CoA, the PFOR:FldA:FqrB complex generated pyruvate via CO2fixation. PFOR was the rate-limiting enzyme in the complex, and nitazoxanide, a specific inhibitor of PFOR ofH. pyloriandCampylobacter jejuni, also inhibited NADP reduction in cell-free lysates. These capnophilic (CO2-requiring) organisms contain gaps in pathways of central metabolism that would benefit substantially from pyruvate formation via CO2fixation. Thus, FqrB provides a novel function in pyruvate metabolism and, together with production of superoxide anions via quinone reduction under high oxygen tensions, contributes to the unique microaerobic lifestyle that defines the epsilonproteobacterial group.