抄録
Glutathione peroxidase (GP EC 1.11.1.9) activity of glutathione S-transferse (GST, EC 2.5.1.18) in rabbit liver was investigated by using hydrogen peroxide (H2O2) and cumene hydroperoxide (C-OOH) as substrates for GP and 1-chloro-2, 4-dinitrobenzene (CDNB) as a substrate for GST.The crude extract from rabbit liver was applied to a diethylaminoethyl (DEAE)-cellulose column equilibrated with 10mM Tris-HCl (pH 8.0) and the absorbed proteins were eluted with the same buffer contaning 0.5 M KCl. The DEAE-non-adsorbed fraction showed 63-87% of the GST activity of the crude extract and 27-36% of the GP activity toward C-OOH, but no GP activity toward H2O2. The DEAE-adsorbed fraction showed 2-11% of the GST activity, 28-48% of the GP activity toward C-OOH and 54-87% of the GP activity toward H2O2. GST and GP in the DEAE-adsorbed fraction could be completely separated as two different activity peaks by gel filtration. This GP had a molecular weight of about 84000, a value similar to those of the well-known selenium-dependent GPs. However, activities of GST and GP in the DEAE-non-adsorbed fraction were eluted as a single peak on gel filtration. The proteins in the peak had a molecular weight of about 52000, a value corresponding to those of the rabbit hepatic GST forms in the previous study.The DEAE-non-adsorbed fraction was resolved into at least seven GST activity peaks (R0, R1, R2, Rx, R3, Rz, R4) by carboxymethyl (CM)-cellulose chromatography or at least eight GST activity peaks (I, II, III, IV, VI, VII, VIII, IX) by isoelectric focusing. These peaks, excepting R2 and VII-IX, showed a high GP activity toward C-OOH.The present study and the previous studies indicate that GST forms composed of Y1 and/or Y3 subunit have a high GP activity toward C-OOH and that these forms account for most of the non-selenium-dependent GP activity in rabbit liver.
