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首页> 外文期刊>Biochimica et Biophysica Acta. Protein Structure and Molecular Enzymology >The pyruvate dehydrogenase complex from thermophilic organisms: thermal stability and re-association from the enzyme components
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The pyruvate dehydrogenase complex from thermophilic organisms: thermal stability and re-association from the enzyme components

机译：嗜热生物的丙酮酸脱氢酶复合物：热稳定性和酶成分的重新结合

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摘要

Examples of pyruvate dehydrogenase complexes, and of its probable precursors, the pyruvate ferredoxin oxidoreductases, both isolated from thermophilic organisms, are described. The pyruvate ferredoxin oxidoreductases are mostly characterized from thermophilic archaea like Sulfolobus solfataricus and Pyrococcus furiosus. They retain their catalytic activity up to 60 and 90 ℃, respectively. Characteristic for the thermophilic nature is a biphasic temperature behavior, reflecting a more stable low temperature and a metastable high temperature form. Another feature is the strong binding of the cofactor thiamin diphosphate. Detailed analysis of thermostable pyruvate dehydrogenase complexes so far only exist for the enzymes from Bacillus stearothermophilus and Thermus flavus. In most respects, especially in the structural features, the enzyme complex from B. stearothermophilus resembles its mesophilic counterparts and only an elevated temperature maximum for the catalytic activity reveals the thermophilic nature. In contrast to this, the more thermostable enzyme complex from T. flavus shows a quite distinct behavior. One single protein chain (M_r = 100 kDa) instead of an α_2β_2 aggregate was found for the pyruvate dehydrogenase (E1) subunits of this enzyme complex. Its catalytic activity is controlled by allosteric regulation, while the enzyme complex from B. stearothermophilus shows no such regulation. Reversible phosphorylation as a regulatory principle of pyruvate dehydrogenase complexes from higher organisms does not take place in the thermophilic enzyme complexes. The overall activity of the enzyme complex from B. stearothermophilus remains stable at 60 ℃ for 50 min while that from T. flavus is active up to 83 ℃. Thermophilic pyruvate dehydrogenase complexes do not spontaneously renature from their separated enzyme components. However, chaperonins from Thermus thermophilus stimulate the reactivation of the enzyme complex from T. flavus.
机译：描述了丙酮酸脱氢酶复合物及其可能的前体丙酮酸铁氧还蛋白氧化还原酶的实例，它们均从嗜热生物体中分离出来。丙酮酸铁氧还蛋白氧化还原酶的主要特征是嗜热古细菌，如Sulfolobus solfataricus和Pyrococcus furiosus。它们分别在高达60和90℃时保持其催化活性。嗜热性质的特征是双相温度行为，反映出更稳定的低温和亚稳态高温形式。另一个特征是辅因子硫胺素二磷酸酯的强结合。到目前为止，仅对来自嗜热脂肪芽孢杆菌和黄热栖热菌的酶进行了热稳定性丙酮酸脱氢酶复合物的详细分析。在大多数方面，特别是在结构特征上，来自嗜热脂肪芽孢杆菌的酶复合物类似于其嗜温对应物，并且仅最高的催化活性最高温度揭示了嗜热性。与此相反，来自黄萎病菌的更热稳定的酶复合物表现出非常不同的行为。发现该酶复合物的丙酮酸脱氢酶（E1）亚基只有一个单蛋白链（M_r = 100 kDa），而不是α_2β_2聚集体。它的催化活性受变构调节作用的控制，而嗜热脂肪芽孢杆菌的酶复合物则没有这种调节作用。可逆磷酸化是来自高级生物的丙酮酸脱氢酶复合物的调控原理，在嗜热酶复合物中不发生。嗜热脂肪芽孢杆菌的酶复合物的整体活性在60℃下保持50分钟稳定，而黄曲霉的酶复合物在83℃时仍具有活性。嗜热丙酮酸脱氢酶复合物不会从其分离的酶组分中自发复性。然而，来自嗜热栖热菌的伴侣蛋白刺激了黄萎病菌的酶复合物的再活化。

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