Abstract
When phenylalanine was treated with the hydrogen peroxide-cupric ions system in acetate buffer (pH 6.0), o-tyrosine, m-tyrosine and p-tyrosine were identified as hydroxylated products. Cupric ions markedly accelerated the decomposition of phenylalanine as compared with other transition metal ions. Radical scavengers, e.g., potassium iodide, dimethyl sulfoxide, formic acid and ethyl alcohol, largely prevented the decomposition of phenylalanine. Superoxide formed from hypoxanthine-xanthine oxidase was found to decompose phenylalanine to some extent. These results suggest that a transient free radical intermediate, formed from hydrogen peroxide, is primarily responsible for the decomposition.
