Title: Pyruvate ferredoxin oxidoreductase from the hyperthermophilic archaeon, Pyrococcus furious, functions as a CoA-dependent pyruvate decarboxylase
Author: Kesen, Ma; Hutchins, A.; Sung, Shi-Jean S.; Adams, Michael W.W.
Date: 1997
Source: In: Proceedings of theNational Academy of Sciences USA. 94: 9608-9613.
Station ID: --
Description: Pyruvate ferredoxin oxidoreductase (POR) has been previously purified from the hyperthermophilic archaeon, Pyrococcus furiosus, an organism that grows optiÂmally at 100°C by fermenting carbohydrates and peptides. The enzyme contains thiamine pyrophosphate and catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA and C02 and reduces P. furiosus ferredoxin. The authors 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 strucÂtural rather than a catalytic role. Ferredoxin was not necesÂsary for the pyruvate decarboxylase activity of POR, nor did it inhibit acetaldehyde production. The apparent Km values for CoA and pyruvate were 0.11 mM and 1.1 mM, respectively, and the optimal temperature for acetaldehyde formation was above 90°C. These data are comparable to those previously determined for the pyruvate oxidation reaction of POR. At 80°C (pH 8.0), the apparent Vm value for pyruvate decarboxÂylation was about 40 percent of the apparent Vm value for pyruvate oxidation rate (using P. furiosus ferredoxin as the electron acceptor). Tentative catalytic mechanisms for these two reÂactions are presented. In addition to POR, three other 2-keto acid ferredoxin oxidoreductases are involved in peptide ferÂmentation 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.
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Citation
Kesen, Ma; Hutchins, A.; Sung, Shi-Jean S.; Adams, Michael W.W. 1997. Pyruvate ferredoxin oxidoreductase from the hyperthermophilic archaeon, Pyrococcus furious, functions as a CoA-dependent pyruvate decarboxylase. In: Proceedings of theNational Academy of Sciences USA. 94: 9608-9613.