Pyruvate oxidoreductase

In Desulfovibrio, as in other strict anaerobes and some aerobic microorganisms, pyruvate is oxidatively decarboxylated by pyruvate oxidoreductase (FOR) according to the following reaction ... 

The conversion of pyruvate to acetyl-CoA is catalysed by pyruvate oxidoreductase in the archaebacteria. The enzyme has been detected and characterised in Halobacterium halobium[i, 2i2 Tp. acidophilum, S. acidocaldarius and Desulfurococcus mobilis[i i], Pyrococcus furiosus [34] and in Methanobacterium thermoautotrophicum [35]. In the halophiles and thermophiles, ferredoxin serves as electron acceptor, whereas the methanogens use the deazaflavin derivative F420. 

Recently, Wahl and Orme-Johnson reported their studies on the characterization and mechanism of the pymvate flavodoxin (ferredoxin) oxidoreductase from Klebsiella pneumoniae and Clostridium thermoacetium (214). These oxi-doreductases appear to be closely related to that from C. acidiurici (215) in that the iron is present in two Fe4S4 clusters, which act as election acceptors in the catalytic mechanism. However the K. pneumoniae and C. thermoaceticum enzymes may be mechanistically distinct from the H. halobium oxidoreductase (213) in that free radical intermediates are not detected for the former enzymic reaction. EPR signals in the Klebsiella or C. thermoaceticum oxidoreductases are only observed in the fully reduced enzyme when the reductants dithionite or pyruvate and CoASH are present (214). The suggested mechanism for the pyruvate oxidoreductase from K. pneumoniae and C. thermoaceticum is initially similar to the mechanism for all TPP enzymes in that decarboxylation of pyra-vate leads to the formation of hydroxyethyl-TPP. Two one-electron transfers to each of the two Fe-S clusters occur on the binding of CoASH. However, the mechanism for the formation of acetyl-CoA from the hydroxyethyl-TPP intermediate and of the CoASH-induced electron transfers is not yet clear. 

Pyruvate flavodoxin oxidoreductase Flavodoxin electron donor to nitrogenase... 

In current industrial practice, benzaldehyde is added to fermenting baker s yeast Saccharomyces cerevisiae) with resultant PAC production occurring from the yeast-derived pyruvate. Typically PAC concentrations of 12-15 g F are produced at yields of 65-70% theoretical in a 10-12 h biotransformation process. [2], Appreciable concentrations of benzyl alcohol are produced as by-product due to oxidoreductase activity in the fermentative yeast. 

Ferredoxins are electron-transfer proteins that can mediate between pyruvate ferredoxin oxidoreductase and hydrogenase. It appears that during the course of the evolution, different types of ferredoxin were recruited for this purpose. In Clostridia, ferredoxins of the 2[4Fe-4S] type are used (Uyeda and Rabinowitz 1971). In T. vaginalis (Chapman et al. 1986) and T. foetus (Marczak et al. 1983), [2Fe-2S] ferredoxins are used. Their axial EPR spectra at g = 1.94,2.02 (Fig. 9.2) resemble those of the ferredoxins that are involved in P450 monooxygenase systems. Similar ferredoxins, with various functions, have been isolated from... 

Uyeda K, Rabinowitz JC. 1971. Pyruvate-ferredoxin oxidoreductase III. Purification and properties of the enzyme. J Biol Chem 246 311-19. 

This enzyme [EC 1.5.1.24], also referred to as A -(1-l-carboxyethyl)-L-ornithine NADP+ oxidoreductase, reversibly catalyzes the reaction of ornithine with pyruvate and NADPH to produce A -(l-carboxyethyl)ornithine, NADP+, and water. Lysine can also serve as a substrate, acting on A , albeit not as effectively as ornithine. 

This enzyme [EC 1.2.7.1], also known as pyruvate ferre-doxin 2-oxidoreductase, catalyzes the reaction of pyruvate with CO enzyme A and oxidized ferredoxin to produce acetyl-CoA, carbon dioxide, and reduced ferredoxin. 

Pyruvateiferredoxin 2-oxidoreductase, PYRUVATE SYNTHASE PYRUVATE FORMATE LYASE PYRUVATE KINASE... 

Mechanism of Action An ant iparasiticthat interferes with the body s reaction to pyruvate ferredoxin oxidoreductase, an enzyme essential for anaerobic energy metabolism. Therapeutic Effect Produces antiprotozoal activity, reducing or terminating diarrheal episodes. 

Both hydrogenase and pyruvate-ferredoxin oxidoreductase activities were inhibited in nitrite-treated cells, and the inhibition was greater with addition of both nitrite and ascorbate (Payne et al., 1990a). However, they noted that enzyme inhibition was not complete. Meyer (1981) also reported incomplete in-... 

Based on the incomplete inhibition of iron-sulfur proteins by nitrite, and the observation that low-spin Fe—NO EPR signals were observed by C. sporogenes cultures that recovered from nitrite treatment, Payne et al. (1990a) concluded that the antimicrobial effect of nitrite or NO cannot be explained by direct inhibition of preformed pyruvate—ferredoxin oxidoreductase or hydrogenase. 

Carpenter, C. E., Reddy, D. S. A., and Cornforth, D. P. (1987). Inactivation of clostridial ferredoxin and pyruvate-ferredoxin oxidoreductase by sodium nitrite. Appl. Environ. Microbiol. 53, 549-552. 

Pyruvate ferredoxin oxidoreductase subunit A, PFORA MLRSFaGKRIPGDGNTAATSV Hrdy and Muller (1995a)... 

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