BTI1, an Azoreductase with pH-Dependent Substrate Specificity

The group II azoreductase BTI1 utilizes NADPH to directly cleave azo bonds in water-soluble azo dyes, including quenchers of fluorescence. Unexpectedly, optimal reduction was dye specific, ranging from a pH of < 5.5 for Janus green B, to pH 6.0 for methyl red, methyl orange, and BHQ-10, to pH > 8.3 for flame orange.