The association of hydrogenase and dithionite reductase activities with the nitrite reductase of Desulfovibrio desulfuricans

Abstract

Summary The membrane bound respiratory nitrite reductase from Desulfovibrio desulfuricans contains six c-type heme groups and catalyzes the six electron reduction of nitrite to ammonia. The purified enzyme required an excess of reducing equivalents for reduction relative to the amount of nitrite consumed in its reoxidation. The anomaly could be accounted for in terms of the presence of low levels of dithionite reductase and hydrogenase activity in the preparation. Dithionite reductase may be an alternate activity of nitrite reductase, whereas hydrogenase was shown to be a contaminant. The contaminating hydrogenase used nitrite reductase as electron acceptor in preference to cytochrome c 3 (M r = 13,000) or benzyl viologen.