Glutathione peroxidase enzyme activity (GPX1)

GPX1 activity was determined by measuring the oxidation of NADPH (nicotinamide adenine dinucleotide phosphate) in the presence of GSH reductase from the supernatants of samples following the procedure described by Chen et al. (2000b) as adopted for meat analysis (Daun et al., 2001). To measure the glutathione peroxidase enzyme activity from blood, samples were taken from the jugular vein from pigs at slaughtering. As an anticoagulant, lithium heparin was used and samples of blood were stored at 4°C until analyzed. Briefly, recorded the oxidation of NADPH by reducing in absorbance at 340 nm. The assay mixture is enclosed with tert.butyl hydroperoxide (0.10 mmol/L), glutathione (0.63 mmol/L), NADPH (0.25 mmol/L), EDTA (5 mmol/L), and glutathione reductase (5 μg/mL) in the potassium phosphate buffer (50 mmol/L; pH 7.6). A mercaptosuccinate-containing blank was used and a serum control was included in every assay. Results are expressed as mg/mL of samples.