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首页> 外文期刊>Biochemistry >A variable-temperature direct electrochemical study of metalloproteins from hyperthermophilic microorganisms involved in hydrogen production from pyruvate.
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A variable-temperature direct electrochemical study of metalloproteins from hyperthermophilic microorganisms involved in hydrogen production from pyruvate.

机译：来自丙酮酸生产氢的超嗜热微生物金属蛋白的可变温度直接电化学研究。

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摘要

The hyperthermophilic bacterium Thermotoga maritima and the hyperthermophilic archaeon Pyrococcus furiosus grow optimally at 80 and 100 degrees C, respectively, by the fermentation of carbohydrates to organic acids, CO2, and H2. Pyruvate is a major source of reductant for H2 production during fermentation, and pyruvate ferredoxin oxidoreductase (POR), a 4Fe-type ferredoxin, and hydrogenase have been previously purified from both species. P. furiosus utilizes a copper-iron-containing POR and a nickel-iron-containing hydrogenase, whereas the POR of T. maritima lacks copper and its hydrogenase lacks nickel. For all four enzymes and for the two ferredoxins, we have determined their reduction potentials (E degrees') and, where possible, thermodynamic parameters associated with electron transfer (delta S degrees and delta H degrees), using differential pulse voltammetry at temperatures ranging from 25 to 95 degrees C. At ambient temperature, the E degrees' values for all six proteins were comparable and spanned less than 50 mV, but their temperature dependence varied dramatically, even between analogous proteins, such that in the physiological-relevant temperature range the E degrees' values became widely separated. In most cases, transition points were observed in E degrees'/temperature profiles, and these generally corresponded with significant increases in catalytic activity, but occurred at lower temperatures in T. maritima than in P. furiosus. The two ferredoxins (and also P. furiosus rubredoxin) had much more negative entropy terms than were calculated for POR and hydrogenase, and these values were also more negative than those previously reported for mesophilic redox proteins. The reduction potentials measured at high temperatures and likely efficiencies of electron transfer between the various proteins were consistent with in vitro activity measurements.(ABSTRACT TRUNCATED AT 250 WORDS)
机译：通过将碳水化合物发酵成有机酸，CO2和H2，高温嗜热细菌马氏嗜热菌和高温嗜热古菌激烈热球菌分别在80和100摄氏度下最佳生长。丙酮酸是发酵过程中产生H2的主要还原剂来源，丙酮酸铁氧还蛋白氧化还原酶（POR），4Fe型铁氧还蛋白和氢化酶先前已从两个物种中纯化。 P. furiosus利用含铜铁的POR和含镍铁的加氢酶，而滨海假单胞菌的POR缺乏铜，而其加氢酶缺乏镍。对于所有四种酶和两种铁氧还蛋白，我们使用差示脉冲伏安法在温度为25至95摄氏度。在环境温度下，所有六种蛋白质的E度值均具有可比性，跨度​​小于50 mV，但它们的温度依赖性变化很大，即使在相似的蛋白质之间也是如此，因此在生理相关温度范围内， E学位的价值观被广泛分开。在大多数情况下，在E度/温度曲线中观察到了转变点，这些转变点通常与催化活性的显着增加相对应，但发生在海象球菌中的温度比狂暴对虾低。两种铁氧还蛋白（还有P. furiosus rubredoxin）的负熵项要比POR和氢化酶计算的要大得多，而且这些值也比以前报道的嗜温氧化还原蛋白的负性要大。高温下测得的还原电位以及各种蛋白质之间可能的电子转移效率与体外活性测量结果一致（摘要截短为250字）

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