Reaction of chlorine dioxide with amino acids and peptides: kinetics and mutagenicity studies.

Chlorine dioxide (ClO2) is currently being considered as an alternate to chlorine as a disinfectant for water treatment. Many organic compounds present in water and food treated with ClO2 are subject to oxidation. 21 amino acids and 3 peptides (L-aspartyl-L-phenylalanine methyl ester (aspartame), L-glycyl-L-tryptophan and L-tryptophylglycine) were studied for their reactivity with ClO2. Chlorine dioxide reacted only with 6 amino acids in 0.1 M sodium phosphate buffer, pH 6.0. The reaction with cysteine, tryptophan and tyrosine was too rapid to be monitored either iodometrically or spectrophotometrically. The reaction with histidine, hydroxyproline and proline was found to be pseudo-first order. ClO2 readily reacted with L-glycyl-L-tryptophan and L-tryptophylglycine but not with aspartame. Mutagenicity studies with the Salmonella microsome assay of the reaction mixtures of ClO2 with those 6 reactive amino acids and the 3 peptides indicated that the reaction products of the 3 peptides, hydroxyproline, and tyrosine exerted mutagenic activity toward both tester strains of TA98 and TA100 in the presence and absence of rat-liver S9 mix.