Effect of DTT on decarboxylation activities toward FA and PCA of purified native CgPAD. DTT (0.2, 0.5, or 1 mM) was added to the reaction mixtures containing ×10 enzyme (1.0-ml final volume) and incubated at 25°C for 20 min. An aliquot (0.1 ml) was withdrawn and added to 0.9 ml of the reaction mixture containing 0.1 M FA or PCA, and the initial velocities of decarboxylation of FA (filled circle) and PCA (open circle) were measured under the standard conditions of enzyme assay. The values obtained from three separate experiments are shown and expressed as percentages, taking the activity of each untreated enzyme as 100%. The bars indicate the standard deviation at each point.