SOD was estimated as per the procedure of Fridovich (1997).
The reaction mixture consists of 3 ml 50 mM potassium
phosphate buffer (pH 7.8), 13 mM methionine, 2 μM
riboflavin, 0.1 mM ethylene diamine tetra acetic acid (EDTA),
75 μM nitroblue tetrazolium (NBT) and 100μlof crude enzyme
extract. A blank (without enzyme and NBT) and a reference
control having NBT but no enzyme were setup to calibrate the
spectrophotometer. All the tubes were exposed to 400W bulbs
(4×100W bulbs) for 15 min and the absorbance was
immediately read at 560 nm using a spectrophotometer. The
percentage inhibition is calculated and 50% inhibition of the
reaction between riboflavin and NBT in the presence of
methionine is taken as 1 unit of SOD activity. The enzyme
activity was expressed as units mg-1 of protein. CAT was
estimated according to the method of Radhakrishnan and
Sarma (1964). The reaction mixture consists of 2.5 ml of 0.1 M
sodium phosphate buffer (pH 7.5) and 2.5 ml of 0.9% (v/v)
Hydrogen peroxide (H2O2). To this mixture 0.5 ml of enzyme
was added and incubated at 28oC for 3 min. The reaction was
then arrested by adding 0.5 ml of 2 N Sulphuric acid (H2SO4)
and the residual H2O2 was titrated with 0.1 N Potassium
permanganate (KMnO4) solution. A blank experiment was
carried out similarly with boiled enzyme extract. Unit of CAT
activity was expressed as ml of 0.1 N KMnO4 equivalent of
H2O2 decomposed/min/mg of protein.