The α-Helical Cap Domain of a Novel Esterase from Gut Shaping the Substrate-Binding Pocket.

The human gut microbiota regulates nutritional metabolism, especially by encoding specific ferulic acid esterases (FAEs) to release functional ferulic acid (FA) from dietary fiber. In our previous study, we observed seven upregulated FAE genes during fecal slurry fermentation using wheat bran. Here, a 29 kDa FAE (FAE) from of was characterized and identified as the type-A FAE. The X-ray structure of FAE has been determined, revealing a unique α-helical domain comprising five α-helices, which was first characterized in FAEs from the gut microbiota. Further molecular docking analysis and biochemical studies revealed that Tyr100, Thr122, Tyr219, and Ile220 are essential for substrate binding and catalytic efficiency. Additionally, Glu129 and Lys130 in the cap domain shaped the substrate-binding pocket and affected the substrate preference. This is the first report on FAE, providing a theoretical basis for the dietary metabolism in the human gut.