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 in vitro fecal
slurry fermentation using wheat bran. Here, a 29 kDa FAE (AsFAE) from Alistipes shahii of Bacteroides was characterized and identified
as the type-A FAE. The X-ray structure of AsFAE 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 A. shahii FAE, providing a theoretical basis for
the dietary metabolism in the human gut.