Table 2. Second-order rate constants for reaction of two-electron oxidants with selenium-containing compounds and enzymes.

Data for radical-mediated oxidation reactions are given in [18,45,46]. Values were determined at room temperature (20–25°C) and pH 7.0–7.4 unless stated otherwise. PC-OOH, phosphatidylcholine hydroperoxide.

Substrate	Oxidant	k2 (M−1·s−1)	Reference
Sec	HOSCN	1.24×106	The present study
Selenocysteine methyl ester	HOSCN	3.7×106	The present study
Selenocystamine	H2O2	9.7×102	[29]
	t-BOOH	1.2×102	[29]
	Cumene-OOH	2.5×102	[29]
	HOSCN	5.8×106	The present study
3-Selenopropionic acid	HOSCN	2.0×106	The present study
Gly-Sec-Gly	HOSCN	1.65×106	The present study
γ-Glu-Sec-Gly	HOSCN	1.7×106	The present study
SeMet	ONOOH	2.4×103	[30]
	HOSCN	2.8×103	The present study
Fmoc—SeMet	HOSCN	1.2×104	The present study
Selenomethylcysteine	HOSCN	<500	The present study
Ebselen	H2O2	4.8	[47]
	ONOOH	2×106 (25°C, pH≥8)	[48]
	HOSCN	~30	The present study
Ebselen–GSH conjugate (selenosulfide)	H2O2	<0.17	[47]
Ebselen selenol	H2O2	47	[47]
		>350	[49]
		2.05×102*	[50]
Ebselen diselenide	H2O2	5.3	[47]
2-(Methylseleno)benzanilide	ONOOH	2.7×103	[51]
GPx1 (per tetramer)	H2O2	4.1×107†	[52]
	t-BOOH	4.2×106†	[52]
	ONOOH	8.0×106	[53]
	ONOOH	1.8×105 (37°C, pH 7.1)	[31]
	HOSCN	5×105	The present study
Oxidized GPx1 (per tetramer)	ONOOH	7.4×105	[53]
Extracellular GPx	H2O2	4.0×107†	[52]
	t-BOOH	2.3×106†	[52]
	PC-OOH	3.4×105†	[52]
Phospholipid hydroperoxide GPx4	PC-OOH	1.5×107†	[52]
Selenoprotein P	PC-OOH	8.6×104†	[52]

*Measured under catalytic conditions in the presence of dehydrolipoate as a cofactor with the tetrameric enzyme; these values are therefore not strictly comparable with direct rate constant data.

†Measured under catalytic conditions in the presence of GSH as a cofactor with the tetrameric enzyme; these values are therefore not strictly comparable with direct rate constant data.