Fig. 3.

Rates of cytochrome c reduction and NADPH oxidation: (a) The rates of cytochrome c reduction by wt and arginine mutants for nNOSred and iNOSred were measured as an increase in absorbance at 550 nm. The reaction mixture contained 5 nM enzyme and 80 uM cytochrome c, and the reaction was initiated by the addition of 100 uM NADPH. Calmodulin (25 nM) was added to nNOSred preparations. (b) The rates of NADPH oxidation were monitored as a decrease in absorbance at 340 nm. (c) Rates of cytochrome c reduction by nNOSred wt and nNOSred R753A were measured at different CaM to enzyme ratios.