Mechanisms of Azo Reduction by<i>Streptococcus faecalis</i>II. The Role of Soluble Flavins

Abstract

1. Using a previously developed continuous assay system, the mechanism of stimulation of Red 2G azo reduction in Streptococcus faecalis by additions of soluble flavins has been investigated.2. Reduced flavins acting as two-electron donors can rapidly reduce Red 2G non-enzymically and the reduced flavins can act as an electron shuttle from NAD(P)H-dependent flavoproteins to the acceptor azo compound.3. Results of inhibition studies were consistent with the direct participation of soluble flavins and the non-involvement of cytochromes in azo reduction.4. Enzyme fractions possessing azo-reductase activity also showed cytochrome c reductase and diaphorase activity, and respired oxygen. Azo reduction under anaerobic conditions may represent a fortuitous, non-enzymic reduction by enzymically-generated reduced flavins; inhibition by oxygen being due to regeneration of the oxidized form.