Table 1.

Competition between enzymatic antioxidants and redox switches for H₂O₂. k_cons and k_sign are pseudo first-order rate constants calculated as the product between k_target+H2O2, the chemical rate constant between H₂O₂ and its target protein, and the concentration of the target protein, either an enzymatic antioxidant or a redox switch. For protein concentrations and rate constant values see [15], [8]. The rather high value for catalase concentration refers to the peroxisome [21].

	ktarget+H2O2 (M−1s−1)	[protein] (µM)	ktarget+H2O2× protein (s−1)
Antioxidant			kcons
Prx	105–107	10	1–100
GPx	6×107	0.2–10	12–600
Catalase	107	103	104
Redox switch			ksign
PTP1B	24	0.01	2.4×10−7
SHP‐2	20	0.01	2.0×10−7
Keap1	140	1	1.4×10−4

Prx – Peroxiredoxin; GPx – Glutathione peroxidase 1.