The effect of a number of amino acids on the catalytic activity of tobacco peroxidase was studied in an in vitro assay system following the optimum pH and temperature conditions. The tested amino acids of two different concentrations (0.2 mM amd 0.8 mM) showed variable responses against the Tobacco peroxidase catalyzed reaction. Amino acids like D-alanine, L-proline, DL-valin, DL-Tryptophan were found to stimulate the activity of peroxidase catalyzed reaction under given condition while certain other amino acids like L-lysine, Arginine, Histidine, Glutamic acid etc. showed no significant effect. Moderate inhibition was observed in case of aspartic acid at relatively higher concentration (0.8mM). However, a very low concentration of L-cysteine (0.2mM) acts as a strong inhibitor of Tobacco Peroxidase activity. Kinetic studies showed that the inhibition type was mixed idnhibition for cystein and noncompetitive inhibition for aspartic acid. The feasible inhibition types of peroxidase oxidation of o-dianisidine in the presence of each inhibitor along with the values of Km and Vmax were determined from Lineweaver-Burk plot.
