Contribution of GOT1 and GOT2 to cellular sulfite production. A. Western Blot of HEK293 lysates confirming knockout of SO, GOT1 and GOT2 (n = 3). B. Sulfite standard curve used for the determination of sulfite concentration from cellular extracts (n = 3). C. Sulfite measurement from cell extracts of WT and SUOX−/− cells with and without addition of purified SO (n = 4). Sulfite levels were normalized to cellular protein concentration. Error bars indicate standard deviation. Two-way ANOVA with Tukey's post-hoc test for pairwise comparisons was performed as indicated. p value: *** <0.001; ** <0.01; * <0.05; ns > 0.05. D. Sulfite measurement from cell extracts of WT, SUOX−/−, GOT1−/−/SUOX−/− and GOT2−/−/SUOX−/− cells (n = 4). Sulfite levels were normalized to cellular protein concentration. Error bars indicate standard deviation. One-way ANOVA with Tukey's post-hoc test for pairwise comparisons was performed as indicated. p value: *** <0.001; ** <0.01; * <0.05; ns > 0.05. E. Relative (isoform-unspecific) GOT activity determined from extracts of WT, SUOX−/−, GOT1−/−/SUOX−/− and GOT2−/−/SUOX−/− cells (n = 3). Values were adjusted to cellular protein concentration and normalized to WT. Error bars indicate standard deviation. One-way ANOVA with Tukey's post-hoc test for pairwise comparisons was performed as indicated. pvalue: *** <0.001; ** <0.01; * <0.05; ns > 0.05. F. Relative cell proliferation of WT, SUOX−/−, GOT1−/−/SUOX−/− and GOT2−/−/SUOX−/− cells determined by MTT assay (n = 3). Values were adjusted to cellular protein concentration and normalized to WT. Error bars indicate standard deviation. One-way ANOVA with Tukey's post-hoc test for pairwise comparisons was performed as indicated. p value: *** <0.001; ** <0.01; * <0.05; ns > 0.05.