FIGURE 2.

Effects of thiols on the inactivation of dehydrogenation by GTN. Panel A, restoration by different thiols of ALDH2-catalyzed dehydrogenation after inactivation by GTN. Plotted are the relative residual activities (v_residual/v_initial) after inactivation by 0.1 mm GTN and the relative restored activities (v_restored/v_initial) after addition of 1 mm DTT, LPA-H₂, or GSH. Initial conditions: 25 μg/ml ALDH2, 0.45 mm acetaldehyde, and 0.4 mm NAD⁺ in 0.2 m potassium P_i (pH 7.4). Panel B, protection by DTT of dehydrogenase activity against GTN-mediated inactivation. The figure shows representative time traces of the ALDH2-catalyzed formation of NADH, as monitored at 340 nm before and after addition of GTN in the presence or absence of DTT. Experimental conditions: 33 μg/ml ALDH2, 0.45 mm acetaldehyde, 0.4 mm NAD⁺, and 0.1 mm GTN with or without 1 mm DTT in 50 mm potassium P_i (pH 7.4).