Table S1.

Catalytic power of XfOhr toward distinct peroxides

Peroxide	kBSA pH 7.4	kBSA pH indep	kOHR pH 7.4	kOHR pH indep	kOHR/kBSA pH indep
H2O2	1.14*	5.7*	3 × 103†	3 × 103†	∼5 × 102
Peroxynitrite	2.6 × 103*	6.5 × 104*	2 × 107†	1 × 108†	∼1.5 × 103
t-BHP	0.37‡	1.85‡	2 × 106§	2 × 106§	∼1.4 × 106

The pH independent (indep) rate constants were calculated considering that the thiolate reacts with protonated peroxide, and taking into account a pK_a value of 6.8 for peroxynitrite (50), and higher than 10.0 for H₂O₂ and t-BHP, and also considering a pK_a for the single thiol in BSA as 8.3 (51) and for the peroxidatic thiol in Ohr as 5.2 (77).

^*Temperature of 37 °C (49).

^†Temperature of 25 °C (this work).

^‡Room temperature (51).

^§Temperature of 37 °C (23).