2.8.1. CAT assay
0.1 ml of the extracted sample was diluted in 0.1 ml of 0.1 M phosphate buffer at a pH value of 6.8 and then incubated in 1.0 ml of the substrate (65 μmol/l hydrogen peroxide in 60 mmol/l sodium potassium phosphate buffer, pH 7.4) at 37 °C for 1 min. The enzymatic reaction was terminated with 1.0 ml of 32.4 mmol/l ammonium molybdate and the yellow complex of molybdate and hydrogen peroxide was spectrophotometrically determined at 405 nm with 3 blanks. The substances in each blank are described as follows: blank I contained 1.0 ml substrate, 1.0 ml molybdate and 0.2 ml of the sample, blank II contained 1.0 ml substrate, 1.0 ml molybdate, and 0.2 ml buffer, and blank III contained 1.0 ml buffer, 1.0 ml molybdate, and 0.2 ml buffer. The activity of CAT (kU/L) was then calculated from the formula: A(sample) − A(blank I)/A(blank II) − A(blank III) * 271.