REDUCTION OF DISULFIDE BONDS IN PEPTIDES AND PROTEINS

We have re-examined the mechanism of disulfide bond reduction in oxidi zed glutathione by CO2. free radicals. The process appears to be a cha in reaction whose initial yield depends on pH and on both peptide and formate ion concentrations, but remains independent on the radiation d ose rate. Kinetic schemes drawn from studies on dithiothreitol are una ble to account for the results obtained with glutathione and proteins, although the disulfide radical anion is the primary intermediate foun d with all compounds. The rate constant for its formation from CO2. an d glutathione is in the same range as those found using proteins, whil e decay pathways are somewhat different. Hypotheses are proposed to ac count for these differences.