Figure 6.

Effect of pH and CO₂ on the PN-dependent oxidation of methionine residues of the tripeptide Ala-Met-Ala. Reaction mixtures (1.0 ml) containing 0.075 mg of the tripeptide (A-M-A) and 3.0 mM PN were incubated in both the absence (open circles) or presence (closed circles) of CO₂: i.e., in 0.3 M K-PO₄ buffer or in bicarbonate buffer prepared as described in Fig. 4. After incubation for 5 min at room temperature, the samples were analyzed for methionine sulfoxide content as described in Materials and Methods.