REACTION OF OZONE WITH AMINO ACIDS AND PROTEINS

The following order of susceptibility of amino acids in aqueous solutions to oxidation by ozone has been found: cysteine, methionine, tryptophan, tyrosine, histidine, cystine, and phenylalanine. The other amino acids found in proteins were unaffected by ozone. The oxidations of tyrosine and histidine were dependent on pH, being greater under alkaline conditions. The oxidation of pancreatic ribonuclease by ozone resulted in a decrease in enzvmic activity. The amino acid residues most affected by treatment with ozone were tyrosine and histidine. Reaction of avidin with ozone caused changes in the absorption spectrum characteristic of the oxidation of tryptophan residues. The biotin binding capacity of avidin was lost after treatment of avidin with ozone. The changes in the absorption spectrum of avidin could be prevented if biotin was bound to the avidin before exposure to ozone. © 1969.