Ascorbate peroxidase activity (APX)

Ascorbate peroxidase was assayed by the method of Nakano and Asada, [28]. The reaction was initiated by adding 50 μl of enzyme extract. A decrease in absorbance was recorded at 290 nm spectrophotometrically for 2 min against a suitable blank. The enzyme activity was calculated, using the molar extinction coefficient (Absorbance of one molar solution) of 2.8 mM^-1 cm^-1 for ascorbate in the standard equation for absorbance. One enzyme unit corresponds to the amount of enzyme required to oxidize one nmol of ascorbic acid min^-1.

The standard equation for absorbance as A = ε × Ɩ × с

Where A is the amount of light absorbed by the sample at a given wavelength, ε is the molar extinction coefficient, Ɩ is the distance that the light travels through the solution, and с is the concentration of the absorbing species.