Characteristics and purification of an oxygen insensitive azoreductase from Caulobacter subvibrioides strain C7-D

An azo dye-degrading bacterium, Caulobacter subvibrioides strain C7-D, semi -constitutively produces an azoreductase that reduced the azo bond of the d yes Acid Orange (AO) 6, AO7, AO8, AO12, Acid Red (AR) 88, AR151, and Methyl Red (MR). This activity was oxygen insensitive. Of the dyes tested, AO7 wa s the best inducer and the most rapidly reduced substrate suggesting that d ye AO7 most closely mimics the natural physiological substrate for this enz yme. The K-m for AO7 was 1 mu M. Purification of the azoreductase from C. s ubvibrioides strain C7-D was achieved through dye-ligand affinity chromatog raphy using the dye Orange-A covalently coupled to an agarose support. The azoreductase is approximately 30 kDa and enzyme studies indicate a single a zoreductase. The optimal activity, pH, cofactor usage, substrate specificit y, molecular weight and K-m characteristics of the enzyme set it apart from other known oxygen-insensitive azoreductases.