Superoxide dismutase (SOD, EC 1.15.1.1) activity was determined
based on inhibition of the photochemical reduction of
nitroblue tetrazolium chloride (NBT). The reaction mixture absorbance
was measured by the Spectrum SP 2000UV
Spectrophotometer at 560 nm and one unit of SOD activity (UA)
was defined as the amount of enzyme required to cause a 50%
reduction in the NBT photo-reduction rate. Results were expressed
as UA/mg P (protein) (Beauchamp & Fridovich, 1971; Giannopolitis
& Ries, 1977).
Catalase (CAT, EC 1.11.1.6) activity was determined through the
reduction capacity of the hydrogen peroxide by the enzyme extract
monitored through absorbance at 240 nm and quantified by its
molar extinction coefficient (36 M/cm). One unit of CAT activity
(UA) was defined as the amount of enzyme required to decompose
H2O2. Results were expressed as lmol H2O2/min/mg P (Beers &
Sizer, 1952).