Fig. 3.

The effects of the NO generator SNP on TPH. Both GST fusion constructs TPH–WT and TPH–CC were prepared and adsorbed to GSH-affinity beads as described and exposed to varying concentrations of SNP ± DTT (1 mm). Enzymes were exposed to SNP at 4°C for 30 min followed by three washes with 50 mmTris-HCl, pH 7.5, to remove the reagent. Residual TPH activity was determined in assays that omitted DTT. The results are presented as % control TPH activity (47.6 and 54.4 nmol · min⁻¹ · mg⁻¹ for WT and CC forms, respectively) and are the mean ± SEM of four independent experiments performed in duplicate. The effects of SNP on both forms of TPH were statistically significant by ANOVA;p < 0.001. The responses of TPH–WT and TPH–CC to SNP did not differ significantly (p > 0.1).