Figure 1.

NOS1 is a PQ diaphorase. (A) Stimulation of NOS1-dependent NADPH oxidation by increasing concentrations of PQ. NADPH oxidation was continuously monitored spectrophotometrically at 340 nm in a microtiter plate format for 1 min. (B) Inhibition of NO formation by increasing concentrations of PQ. The same microtiter plates used above were left at room temperature for 5 hr, and then an aliquot was assayed for total nitrite and nitrate. (C) Anaerobic reduction of PQ to its cation radical (PQ⨥) by NOS1. Formation of PQ⨥ was followed at 600 nm for 3 min. (D) Hanes plot (K_m and V_max values) for the PQ reductase activity of rat NOS1.