Mechanisms of Azo Reduction by Streptococcus faecalis 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.