Cleavage of the disulfide bonds of cystine and oxidized glutathione by phosphorothioate

Abstract

The scission of disulfide bonds in low molecular weight model compounds such as cystine and oxidized glutathione is presented. The experimental results obtained suggest that the reaction between phosphorothioate and cystine proceeds according to the equation RSSR + ( O 3 PS) ⇄ ( RS) + ( RSSPO 3). It was shown that this reaction is reversible in the pH range 4.5 to 9.5. The reaction is also pH dependent, and has a maximum rate at pH 8.0. Equilibrium constants have been calculated from the results obtained from the reaction with N-ethylmaleimide and found to be 2.2 × 10 −1 liter/mole at pH 8.0, and 9 × 10 −2 liter/mole at pH 6.8. Pertinent data concerning the reaction of phosphorothioate with several sulfhydryl reagents are included.