(2) Peroxidase
Peroxidase catalyses the formation of I2 and this is followed by instantaneous formation of periodide when there is an excess of iodide substrate. Nearly all the enzyme- generated I2 is bound as I3ˉ . Periodide can be spectrophotometrically determined at its absorption maxima of 353 nm and the yield of I3ˉ is directly proportional to the concentration of peroxidase in the reaction mixtures [29, 32].