Glycogen phosphorylase a and b are irreversibly inactivated by oxidation with the disulfide cystamine. The mechanism is complex and involves oxidation of at least two classes of sulfhydryl groups. The oxidation of one or more of the first class of 4 f 1 sulfhydryl groups is reversible, but the equilibrium constant for the oxidation is so unfavorable (1 X that the micromolar concentrations of cy...
