MOLECULAR MECHANISM OF PYRUVATE-FERREDOXIN OXIDOREDUCTASES BASED ON DATA OBTAINED WITH THE CLOSTRIDIUM-PASTEURIANUM ENZYME

Pyruvate-ferredoxin oxidoreductase oxdises pyruvate in many fermentati ve microorganisms. The enzyme from Clostridium pasteurianum is an air- sensitive homodiner of 2x120000 daltons, for which pyruvate is the bes t substrate found among several alpha-ketoacids. Each submit contains eight iron atoms in two [4Fe-4S] clusters. Two distinct EPR signals, p ossibly associated with two ligand environments, arise from one of the se clusters. Binding of pyruvate does not generate a radical. The resu lts reported suggest a scheme for the electron flow in pyruvate ferred oxin oxidoreductases according to which the detailed reaction mechanis m depends on the number (even or odd) of [4Fe-4S] clusters present in a given enzyme.