Catalyzes the reductive cleavage of azo bond in aromatic azo compounds to the corresponding amines. Uses preferentially NADPH rather than NADH as an electron donor for its activity. The enzyme reductively cleaved Orange II and carboxy-Orange II, and can also reduce several sulfonated structural analogs, which carry a hydroxy group in the 2 position of the naphthol ring. Optimum pH is 6.2-6.8. Optimum temperature is 41 degrees Celsius. Monomer. Belongs to the NmrA-type oxidoreductase family. Azoreductase type 3 subfamily.