Comparison of the toxicity of the dyes Sudan II and Sudan IV to catalase

The mechanisms of the toxicity of Sudan dyes to the key antioxidant enzyme catalase (CAT) were investigated by spectroscopic methods, calorimetry techniques, enzyme activity assay, and molecular docking. Results showed that Sudan dyes bound to CAT through hydrophobic force, which changed the microenvironment of tryptophan and tyrosine residues, leading to a conformational alteration and shrinkage of the protein. Enzyme activity assay and molecular docking revealed that the activity of CAT was slightly inhibited in the presence of Sudan dyes. In comparison, the binding of Sudan II with CAT was slightly stronger than Sudan IV. Also, Sudan II and Sudan IV showed a different impact on the microenvironment of aromatic amino acid residues. But the dyes had very similar effects on conformation and activity of the protein. This work provides an essential reference for the evaluation of Sudan dyes' effects on body's antioxidant defense system and safe use of Sudan dyes.