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Molecular mechanism of pyruvate-ferredoxin oxidoreductases based on data obtained with the Clostridium pasteurianum
J M Moulis1, V Davasse, J Meyer
1CEA Département de Biologie Moléculaire et Structurale, Laboratoire des Métalloprotéines, Grenoble, France.
Abstract:
Pyruvate-ferredoxin oxidoreductase oxidises pyruvate in many fermentative microorganisms. The enzyme from Clostridium pasteurianum is an air-sensitive homodimer of 2x120000 daltons, for which pyruvate is the best substrate found among several alpha-ketoacids. Each subunit contains eight iron atoms in two [4Fe-4S] clusters. Two distinct EPR signals, possibly associated with two ligand environments, arise from one of these clusters. Binding of pyruvate does not generate a radical. The results reported suggest a scheme for the electron flow in pyruvate ferredoxin oxidoreductases according to which the detailed reaction mechanism depends on the number (even or odd) of [4Fe-4S] clusters present in a given enzyme.