Catalysis of nitrite generation from nitroglycerin by glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

Abstract Vascular relaxation to nitroglycerin (glyceryl trinitrate; GTN) requires its bioactivation by mechanisms that remain controversial. We report here that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the release of nitrite from GTN. In assays containing dithiothreitol (DTT) and NAD + , the GTN reductase activity of purified GAPDH produces nitrite and 1,2-GDN as the major products. A v max of 2.6 nmol min − 1  mg − 1 was measured for nitrite production by GAPDH from rabbit muscle and a GTN K M of 1.2 mM. Reductive denitration of GTN in the absence of DTT results in dose- and time-dependent inhibition of GAPDH dehydrogenase activity. Disulfiram, a thiol-modifying drug, inhibits both the dehydrogenase and GTN reductase activity of GAPDH, while DTT or tris(2-carboxyethyl)phosphine reverse the GTN-induced inhibition. Incubation of intact human erythrocytes or hemolysates with 2 mM GTN for 60 min results in 50% inhibition of GAPDH’s dehydrogenase activity, indicating that GTN is taken up by these cells and that the dehydrogenase is a target of GTN. Thus, erythrocyte GAPDH may contribute to GTN bioactivation.