Iron-sulfur proteins pyruvate-ferredoxin oxidoreductase

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. 

The molar masses of the 2-oxoacid ferredoxin oxidoreductases are 200,000-300,000 g/mol and they are composed of four subunits of the kind a2p2. It has been shown that halobacteria have only these systems of 2-oxoacid ferredoxin oxidoreductases. The two enzymes of H. halobium (pyruvate and oxoglutarate) were isolated and characterized by Kerscher and Oesterhelt (1981a). These systems proved to be thiamin diphosphate-containing iron-sulfur proteins. The relative stability of the halobacterial enzymes enabled detailed analysis of the various steps of the catalytic cycles (Kerscher and Oesterhelt, 1981b), demonstrating two distinct steps of one-electron transfer reactions. 

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