Extended Data Fig. 2. Specific serine protease activity assays in both high PA human and high PA humanized mouse fecal supernatants.

a, Specific serine protease activity of human fecal samples. Using an enzyme preferential substrate assay, fecal trypsin (*p=0.049, **p=0.004), chymotrypsin (**p=0.004) and pancreatic elastase (*p=0.03, **p=0.007) activities were increased in fecal supernatants generated from high PA individuals compared to both low PA PI-IBS and healthy volunteers (One-way ANOVA, multiple comparisons Kruskal-Wallis, n=6 FSNs/group). b, Specific activity of serine proteases in humanized mice and germ-free mice. Mice humanized with high PA microbiota had increased chymotrypsin (*p=0.049, **p=0.004), pancreatic elastase (healthy **p=0.008, low PA PI-IBS **p=0.002) and neutrophil elastase activity (*p=0.01, **p=0.002) in fecal supernatants compared to either healthy volunteer or low PA PI-IBS humanized mice. Decreased trypsin (healthy **p=0.008, low PA PI-IBS **p=0.002), chymotrypsin (**p=0.002), pancreatic elastase (**p=0.002) and neutrophil elastase (*p=0.02, **p=0.004) activity were seen in healthy and low PA PI-IBS humanized mice compared to the germ-free (GF) state. (One-way ANOVA, multiple comparisons Kruskal-Wallis, n=3 mice tested/humanization, 6 humanizations/phenotype, n=6 germ-free mice). Boxplots: lower, middle and upper hinges correspond to 25^th, 50^th and 75^th percentiles. Upper and lower whiskers extend to the largest and smallest value no further than 1.5 * IQR from the respective hinge.