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Novel enzymes involved in peptide fermentation from hyperthermophilic archaea.

机译：涉及高嗜热古细菌肽发酵的新型酶。

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摘要

The goal of this research was to elucidate the catabolic pathway of peptide fermentation in hyperthermophilic archaea, a group of microorganisms able to grow optimally at 80{dollar}spcirc{dollar}C and above. In particular, the studies described here focused on identification and characterization of the enzymes catalyzing the formation of various organic acids, the end products of fermentation from their corresponding 2-keto acids, which are the transaminated products from various amino acids.; Three novel 2-keto acid ferredoxin oxidoreductases have been purified and characterized from the hyperthermophilic archaea, Pyrococcus furiosus, Thermococcus litoralis and Thermococcus strain ES-1. These are indolepyruvate ferredoxin oxidoreductase (IOR), 2-ketoisovalerate ferredoxin oxidoreductase (VOR) and 2-ketoglutarate ferredoxin oxidoreductase (KGOR), all of which are analogous to pyruvate ferredoxin oxidoreductase and catalyze the oxidative decarboxylation of 2-keto acids. IOR and VOR preferentially use as substrates the aromatic and branched-chain 2-keto acids, respectively, whereas KGOR is very specific for 2-ketoglutarate. IOR and VOR are the first examples of this type of oxidoreductase to be described while KGOR appears to be different from the one characterized previously from a mesophilic archaeon. Biochemical and spectroscopic characterizations of IOR, VOR and KGOR demonstrated that they are closely related and belong the same protein family. In addition, these are also iron-sulfur proteins and their catalytic mechanisms, which are distinct from that of pyruvate dehydrogenase, resemble that of a well-studied pyruvate ferredoxin oxidoreductase from a mesophilic archaeon.; Two unique ADP-dependent acetyl-coenzyme A (CoA) synthetase isoenzymes were also purified and characterized from hyperthermophilic archaeon, Pyrococcus furiosus. These differ in their substrate specificities and catalyze the formation of various organic acids from their corresponding CoA-derivatives, which are the products of the oxidoreductases described above. The molecular and catalytic properties of this type of enzyme are very different from the conventional AMP-forming acetyl-CoA synthetase found in many mesophilic microorganisms.
机译：这项研究的目的是阐明高嗜热古细菌中肽发酵的分解代谢途径，这组微生物能够在80℃以上的温度下最佳生长。特别是，这里描述的研究集中于鉴定和表征催化各种有机酸形成的酶，这些酶是由它们相应的2-酮酸发酵产生的终产物，它们是各种氨基酸的转氨产物。三种新型的2-酮酸铁氧还蛋白氧化还原酶已从嗜热古细菌，激烈热球菌，滨海热球菌和热球菌菌株ES-1中纯化并鉴定。它们是吲哚丙酮酸铁氧还蛋白氧化还原酶（IOR），2-酮异戊酸铁氧还蛋白氧化还原酶（VOR）和2-酮戊二酸铁氧还蛋白氧化还原酶（KGOR），所有这些都类似于丙酮酸铁氧还蛋白氧化还原酶并催化2-的氧化脱羧反应。 IOR和VOR分别优先使用芳香族和支链的2-酮酸作为底物，而KGOR对2-酮戊二酸酯非常特异。 IOR和VOR是将要描述的这种类型的氧化还原酶的第一个例子，而KGOR似乎与先前从嗜温古细菌中表征的那个不同。 IOR，VOR和KGOR的生化和光谱表征表明它们密切相关并且属于同一蛋白质家族。另外，这些也是铁-硫蛋白，其催化机理与丙酮酸脱氢酶不同，类似于对嗜温古细菌中丙酮酸铁氧还蛋白氧化还原酶的研究。两种独特的ADP依赖性乙酰辅酶A（CoA）合成酶同工酶也被纯化，并从嗜热古菌激烈热球菌（Pyrococcus furiosus）中进行了表征。它们的底物特异性不同，并催化由它们相应的CoA衍生物形成各种有机酸，CoA衍生物是上述氧化还原酶的产物。这种酶的分子和催化特性与许多嗜温微生物中发现的传统的形成AMP的乙酰辅酶A合成酶非常不同。

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  • 作者

    Mai, Xuhong.;

  • 作者单位

    University of Georgia.;

  • 授予单位 University of Georgia.;
  • 学科 Chemistry Biochemistry.; Biophysics General.; Biology Microbiology.
  • 学位 Ph.D.
  • 年度 1996
  • 页码 205 p.
  • 总页数 205
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生物化学;生物物理学;微生物学;
  • 关键词

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