Pyruvate ferredoxin oxidoreductase from the hyperthermophilic archaeon, Pyrococcus furiosus, functions as a CoA-dependent pyruvate decarboxylase
Pyruvate ferredoxin oxidoreductase from the hyperthermophilic archaeon, Pyrococcus furiosus, functions as a CoA-dependent pyruvate decarboxylase
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DOI：
10.1073/pnas.94.18.9608
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发表时间：
1997-09-02
影响因子：
11.1
通讯作者：
Adams, MWW
中科院分区：
文献类型：
--
作者：
Ma, K;Hutchins, A;Adams, MWW
丙酮酸铁氧还蛋白氧化还原酶(FOR)是从高温嗜热古生菌--金黄色葡萄球菌中提纯的，它是一种发酵碳水化合物和多肽，在100℃下生长最适的生物体。该酶含有焦磷酸硫胺素，催化丙酮酸氧化脱羧为乙酰辅酶A和二氧化碳，并还原铁氧化还蛋白。我们证明，该酶还催化丙酮酸在辅酶A依赖的反应中生成乙醛，Desulfocoase A取代辅酶A，说明辅酶A不是丙酮酸脱羧酶活性所必需的，它也不抑制乙醛的产生。CoA和丙酮酸的表观K-m值分别为0.11 mm和1.1 mm，生成乙醛的最适温度在90℃以上，这些数据与以前测定的丙酮酸氧化反应的数据相当。在80℃(pH 8.0)下，丙酮酸脱羧酶的表观V-m值约为丙酮酸氧化速率表观V-m值的40%(以呋喃拟青霉铁氧还蛋白为电子受体)，对这两个反应的催化机理进行了初步探讨。此外，还有另外三种2-酮基酸性铁氧还蛋白氧化还原酶参与了嗜热古菌的多肽发酵，推测这些氧化还原酶在体内产生的各种醛是由两种醛利用酶--乙醇脱氢酶和醛铁氧还蛋白氧化还原酶利用的，这两种酶的生理作用尚不清楚。
Pyruvate ferredoxin oxidoreductase (FOR) has been previously purified from the hyperthermophilic archaeon, Pyrococcus furiosus, an organism that grows optimally at 100 degrees C by fermenting carbohydrates and peptides, The enzyme contains thiamine pyrophosphate and catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA and CO2 and reduces P. furiosus ferredoxin, Here we show that this enzyme also catalyzes the formation of acetaldehyde from pyruvate in a CoA-dependent reaction, Desulfocoenzyme A substituted for CoA showing that the cofactor plays a structural rather than a catalytic role, Ferredoxin was not necessary for the pyruvate decarboxylase activity of FOR, nor did it inhibit acetaldehyde production, The apparent K-m values for CoA and pyruvate were 0.11 mM and 1.1 mM, respectively, and the optimal temperature for acetaldehyde formation was above 90 degrees C, These data are comparable to those previously determined for the pyruvate oxidation reaction of FOR. At 80 degrees C (pH 8.0), the apparent V-m value for pyruvate decarboxylation was about 40% of the apparent V-m value for pyruvate oxidation rate (using P. furiosus ferredoxin as the electron acceptor), Tentative catalytic mechanisms for these two reactions are presented, In addition to FOR, three other 2-keto acid ferredoxin oxidoreductases are involved in peptide fermentation by hyperthermophilic archaea, It is proposed that the various aldehydes produced by these oxidoreductases in vivo are used by two aldehyde utilizing enzymes, alcohol dehydrogenase and aldehyde ferredoxin oxidoreductase, the physiological roles of which were previously unknown.