Studies on Radiolysis of Amino Acids and Proteins II. On Radiolytic Deamination of Amino Acids in Aqueous Solutions by Gamma Irradiation

Abstract

Radiolytic deamination of amino acids in aqueous solutions by gamma irradiation was studied. Ammonia yield by the deamination of amino acids was observed to remain almost constant for a wide range of irradiation doses. The yield was also found to increase with the increase concentration of the amino acid. Radio-sensitiveness of α-amino acid to the deamination was proved to be larger than that of β-amino acid. ω-Amino acid seems to be very resistant to γ-rays and a amino group of amino sulfonic acid was more stable than that of amino carboxylic acid. α-Keto acid was found to be produced from its parent amino acid by γ-irradiation in the aerated acqueous solution. Pyruvic acid, α-keto-isovaleric acid and α-ketoglutaric acid were identified from characteristics of ultraviolet absorption spectra and chromatographic behaviours of their corresponding 2, 4-dinitrophenylhydrazones. The reaction yield of α-ketoglutaric acid obtained from glutamic acid by γ-irradiation was found to vary with γ-ray doses exponentially. The yield of decomposed α-alanine was identical stoichimetrically with that of liberated ammonia. The yield of pyruvic acid found from alaine, however, was not same as of decomposed alanine. The reaction product of leucine with hydrogen peroxide or with a Fenton's reagent was some-what different from that with γ-irradiation. From these results, a mechanism of oxidative deamination of amino acid was proposed.