A variable-temperature direct electrochemical study of metalloproteins from hyperthermophilic microorganisms involved in hydrogen production from pyruvate.
A variable-temperature direct electrochemical study of metalloproteins from hyperthermophilic microorganisms involved in hydrogen production from pyruvate.
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DOI：
10.1021/bi00021a030
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发表时间：
1995-05
期刊：
影响因子：
2.9
通讯作者：
E. T. Smith;J. Blamey;Z. Zhou;M. Adams
中科院分区：
文献类型：
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作者：
E. T. Smith;J. Blamey;Z. Zhou;M. Adams
通过将碳水化合物发酵为有机酸、CO2 和 H2，超嗜热细菌 Thermotoga maritima 和超嗜热古菌 Pyrococcus Furiosus 分别在 80 和 100 摄氏度下生长最佳。丙酮酸是发酵过程中产生氢气的还原剂的主要来源，丙酮酸铁氧还蛋白氧化还原酶 (POR)（一种 4Fe 型铁氧还蛋白）和氢化酶先前已从这两个物种中纯化。 P. Furiosus 利用含铜-铁的 POR 和含镍-铁的氢化酶，而 T. maritima 的 POR 缺乏铜，并且其氢化酶缺乏镍。对于所有四种酶和两种铁氧还蛋白，我们在 25 至 95 摄氏度的温度下使用差分脉冲伏安法测定了它们的还原电位（E 度），并在可能的情况下确定了与电子转移相关的热力学参数（δ S 度和 δ H 度）。在环境温度下，所有六种蛋白质的 E 度值具有可比性，跨度小于 50 mV，但它们的温度依赖性变化很大，即使在类似蛋白质之间也是如此，因此在在与生理相关的温度范围内，E 度值之间的差异很大。在大多数情况下，在 E 度/温度曲线中观察到转变点，这些转变点通常与催化活性的显着增加相对应，但在 T. maritima 中发生的温度低于 P. Furiosus 中的温度。这两种铁氧还蛋白（以及 P.furiosus rubredoxin）的负熵项比 POR 和氢化酶的计算值要大得多，并且这些值也比之前报道的嗜温氧化还原蛋白的负熵项更大。在高温下测量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。（摘要截断为 250 字）
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)