FIGURE 8.

Effects of N-acetylserotonin and dicoumarol on sepiapterin reduction and redox cycling by human recombinant sepiapterin reductase. Sepiapterin reductase activity was measured by decreases in sepiapterin absorbance at 420 nm. Redox cycling was measured by the formation of superoxide anion in enzyme assays in the presence of 100 μm menadione. Note that both N-acetylserotonin and dicoumarol inhibit sepiapterin reduction (IC₅₀ = 2.6 and 0.2 μm, respectively) but not redox cycling activity. Sepiapterin reduction was analyzed by changes in absorbance of sepiapterin at 420 nm.