REACTIONS OF OXYGEN RADICALS WITH SYNTHETIC PROLINE-RICH OLIGOPEPTIDES

The reaction of two synthetic oligopeptide analogs of the hinge-like r egion of rabbit IgG - CPPPEL (P-Cys) and APPPEL (P-Ala) - with superox ide anion (O2 radical-anion) was investigated P-Cys (but not P-Ala) re acted with O2 radical-anion, although the reaction rate constant was m uch lower than that for superoxide dismutase. P-Cys spontaneously form ed clusters in water solutions which were reactive with O2 radical-ani on, these were the only active form of the peptide. P-Ala does not for m active clusters. Mixed solutions of P-Cys and P-Ala contained a prod uct with increased affinity for O2 radical-anion, probably due to co-a ggregation of the peptides. Incubation of the mixture at 56-degrees-C led to its inactivation. The presence of ZnCl2 changed the pathway of O2 radical-anion utilization by P-Cys. Possible connections between P- Cys activity and its aggregated form are discussed.