Figure 4
Rat INMT is not sufficient for tryptamine methylation. (a) Western blot showing expression of GST-INMT fusion proteins of rat, rabbit and human INMTs in E. coli. The control lane is showing expression of an empty vector GST, where INMT is absent. Uncropped image of the western blot is included as Supplementary Figure S3. (b) Radiometric enzyme assays with extracts from E. coli expressing GST-fusion recombinant rat, rabbit, and human INMT proteins. Plots show the average of 6 individual experiments per condition with error bars indicating standard deviations. CPM = counts per minute. The assay revealed tryptamine-dependent activity of both rabbit INMT (average SA = 350.9 ± 23.08, 95% CI of mean = 326.7–375.1) and human INMT (average SA = 171.8 ± 12.38, 95% CI of mean = 158.8–184.8). Activity was significantly higher in rabbit INMT relative to human INMT (t = 16.75, mean difference = 179.1, 95% CI = 154.3–204, p < 0.0001). The activity of rat INMT (average SA = 0.64 ± 0.21, 95% CI of mean = 0.42–0.85) was significantly lower (t = 3.68, mean difference = − 0.48, 95% CI = − 0.77 to − 0.19, p = 0.004) than empty vector GST extracts (average SA = 1.12 ± 0.24, 95% CI of mean = 0.86–1.37).
