Cytochrome C Nitrite Reductase from Sulfurospirillum Deleyianum and Wolinella Succinogenes

Abstract

Within the biogeochemical nitrogen cycle NxOy compounds function as electron acceptors of anaerobic respiratory chains. Prokaryotes carry out their energy conservation during reduction of these nitrogen compounds, and use complex transition metal enzymes for their transformation [1,2]. Dissimilatory nitrate reduction proceeds via two different pathways, i.e. denitrification, and nitrate- ammonification (Scheme 1). In denitrification, the nitrite reductase is either a cytochrome cd 1, or a copper protein [3,4]. During nitrate-ammonification nitrate is reduced to nitrite as the only liberated intermediate that is subsequently converted to ammonia in a six-electron step by a cytochrome c nitrite reductase [4]. H2 and formate are the predominant electron donors that are oxidized by nitrate-ammonifying bacteria [5–7]. Eisenmann et al. [8] reported on the use of sulfide as electron donor to support bacterial growth by nitrate-ammonification, thus connecting the biogeochemical cycles of nitrogen and sulfur.