The Intestinal Redox System and Its Significance in Chemotherapy-Induced Intestinal Mucositis

Table 1

Major oxidoreductive enzymatic reactions of oxidoreductases in intestine.

Enzyme name	Enzymatic reaction	Cofactor
NADPH oxidase	NADPH+2 O2=2 O2^.-+NADP^+ +H^+
Xanthine dehydrogenase	H2O+xanthine+O2=H2O2+urate	[2Fe-2S] cluster, FAD, Mo-molybdopterin
Nitric oxide synthase	H^++4 O2+3 NADPH+2 L-arginine=4 H2O+L-citrulline+3 NADP^++ 2NO	Heme, FAD, FMN, tetrahydrobiopterin (BH4)
Myeloperoxidase	Chloride+H^++H2O2=H2O+hypochlorous acid	Ca^2+, Heme b
Catalase	2H2O2=2H2O+O2	Heme, NADP^+
Superoxide dismutase
SOD1	2H^++2 O2^.-=H2O2+O2	Zn^2+, Cu^+
SOD2		Mn^2+
SOD3		Zn^2+, Cu^+
Glutathione peroxidase
GPX1~3, 5~8	2 glutathione+H2O2=glutathione-2S+2 H2O
GPX4	1 hydroperoxy polyunsaturated fatty acid+2 glutathione=1 hydroxy polyunsaturated fatty acid+glutathione-2S+H2O
Peroxiredoxin
PRDX-1~5	[thioredoxin]-dithiol+1 hydroperoxide=[Thioredoxin]-2S+1 alcohol+H2O
PRDX-6	1 hydroperoxide+2 glutathione=1 alcohol+glutathione-2S+H2O
Heme oxygensae
HO-1	Heme b+3 O2+3 reduced [NADPH-hemoprotein reductase]=Biliverdin IXα+CO+Fe^2++H^++3 H2O+3 oxidized [NADPH-hemoprotein reductase]
HO-2