Enzymatic Characterization and Structural Analysis of Arylesterase from Lacticaseibacillus rhamnosus GG

To obtain novel esterases from probiotic bacteria, the genome of the probiotic Lacticaseibacillus rhamnosus GG (LGG) was analyzed, and the arylesterase gene (LggAE) from LGG was cloned and heterologously expressed. The expressed enzyme was subjected to affinity purification for enzymatic characterization and structural analysis. The results revealed that the optimal pH of the arylesterase was 7.5, which maintained more than 70% of its activity at pH 7.0–10.0. The optimal temperature of LggAE was 50 ℃. LggAE preferentially hydrolyzed medium-chain p-nitrophenol esters, and the most suitable substrate for it was p-nitrophenol octanoate. LggAE was stable at 40 ℃. The enzymatic activity of LggAE was improved by 17.3% in the presence of ethylene glycol. LggAE was tolerant to DMSO. LggAE retained 39.1%–71.0% of its activity in the presence of sodium citrate or NaCl at high concentrations. The enzymatic activity of LggAE was significantly inhibited by sodium deoxycholate at high temperatures. Structural analysis showed that the substrate binding pocket of LggAE was a small hole mainly composed of aliphatic hydrophobic residues.