Systematic studies of the interactions between a model polyphenol compound and microbial β-glucosidases

Abstract

Lignin is a major obstacle for cost-effective conversion of cellulose into fermentable sugars. Non-productive adsorption onto insoluble lignin fragments and interactions with soluble phenols are important inhibition mechanisms of cellulases, including β-glucosidases. Here, we examined the inhibitory effect of tannic acid (TAN), a model polyphenolic compound, on β-glucosidases from the bacterium Thermotoga petrophila (TpBGL1 and TpBGL3) and archaeon Pyrococcus furiosus (PfBGL1). The results revealed that the inhibition effects on β-glucosidases were TAN concentration-dependent. TpBGL1 and TpBGL3 were more tolerant to the presence of TAN when compared with PfBGL1, while TpBGL1 was less inhibited when compared with TpBGL3. In an attempt to better understand the inhibitory effect, the interaction between TAN and β-glucosidases were analyzed by isothermal titration calorimetry (ITC). Furthermore, the exposed hydrophobic surface areas in β-glucosidases were analyzed using a fluorescent probe and compared with the results of inhibition and ITC. The binding constants determined by ITC for the interactions between TAN and β-glucosidases presented the same order of magnitude. However, the number of binding sites and exposed hydrophobic surface areas varied for the β-glucosidases studied. The binding between TAN and β-glucosidases were driven by enthalpic effects and with an unfavorable negative change in entropy upon binding. Furthermore, the data suggest that there is a high correlation between exposed hydrophobic surface areas and the number of binding sites on the inhibition of microbial β-glucosidases by TAN. These studies can be useful for biotechnological applications.

Toxicity and Toxicokinetics of Amygdalin in Maesil (Prunus mume) Syrup: Protective Effect of Maesil against Amygdalin Toxicity

“…It is likely that complex functional Maesil syrup matrix play a role in defense against enzymatic degradation. 42,43 This tendency was also observed in toxicokinetic results.…”

“…Meanwhile, the metabolic degradation profile of amygdalin in Maesil syrup slows retarded enzymatic conversion of amygdalin to prunasin only after long-term exposure, 6–24 h, which was not found when amygdalin was reacted with other main components, such as glucose and fructose mixture, polyphenol (as gallic acid), organic acids, or glucose, fructose, polyphenol, and organic acid mixture (Supplementary Figure 2). It is likely that complex functional Maesil syrup matrix play a role in defense against enzymatic degradation. , This tendency was also observed in toxicokinetic results.…”