Figure 2.

Time-course for the reactivation of papain-Cys25–S–S–CH₃ by immobilized DTBA (100 equiv) and a solution-phase disulfide catalyst (30 mol%). Reactions were performed in 0.10 M imidazole–HCl buffer, pH 7.0, containing EDTA (2 mM). (A) Unstrained disulfide catalysts. Cystamine (3): $k_{\text{cat}}^{\text{obs}}/k_{\text{uncat}}^{\text{obs}}=1.9$; DTBA^ox (1): $k_{\text{cat}}^{\text{obs}}/k_{\text{uncat}}^{\text{obs}}=1.6$; DTT^ox (2): $k_{\text{cat}}^{\text{obs}}/k_{\text{uncat}}^{\text{obs}}~1.0$; βME^ox (4): $k_{\text{cat}}^{\text{obs}}/k_{\text{uncat}}^{\text{obs}}~1.0$. (B) Strained disulfide catalysts. BMC^ox (5): $k_{\text{cat}}^{\text{obs}}/k_{\text{uncat}}^{\text{obs}}=4.3$; lipoic acid (6): $k_{\text{cat}}^{\text{obs}}/k_{\text{uncat}}^{\text{obs}}=1.9$. Data for immobilized DTBA alone are shown in both panels.