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A 22 kDa xylanase (AtXyl1) from Aspergillus tamarii was purified by two chromatographic steps and presented preference for oat spelt (OSX), birchwood (BrX) and beechwood (BeX) xylans respectively, as substrates. AtXyl1 displays the highest activity at pH 5.5 and 55 °C and showed tolerance over a range of different phenolic compounds. The activity of AtXyl1 was not inhibited when the enzyme was incubated with ferulic acid (FA) using OSX or BrX as substrate. On the other hand, the incubation of AtXyl1 with BeX and FA resulted in an increase in enzyme activity. The molecular docking of a GH11 xylanase from Aspergillus niger with FA showed the preference for binding within the catalytic site. The position of FA was based on the presence or absence of a complexed substrate. When the enzyme from A. niger was docked in the absence of xylan in its crystal structure, FA interacted with Tyr164 and a water molecule. For the enzyme socked with xylo-oligosaccharides, FA interacted with Ser94, Tyr89 and the xylo-oligosaccharide present in the catalytic site. Thermodynamic parameters from the reaction of AtXyl1 with different xylans and FA indicate that FA can cause a conformational change in the enzyme, and this can influence the substrate fitting and makes the enzyme tolerant or active toward the substrate. Our findings suggest that enzyme activation or tolerance to phenolic compounds can be correlated to subtle changes in enzyme conformation due to the presence of the phenolic compound., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Aims: This study evaluated the mechanisms involved in the chemopreventive effects of a mucoadhesive formulation (FITOPROT), containing curcuminoids from Curcuma longa L. (Zingiberaceae) and Bidens pilosa L. (Asteraceae) extract, against 5-FU-induced cellular toxicity using an in vitro oral mucositis model., Main Methods: Effects of FITOPROT on 5-FU-induced cytotoxicity in HaCaT and SSC-4 cells were evaluated by MTT assay. For mechanistic analyses, HaCaT cells were first pretreated with FITOPROT (0.005%) for 24h followed by treatment with FITOPROT and simultaneously exposed to 5-FU (10μg/mL) for additional 24h., Key Findings: FITOPROT was able to protect HaCaT cells from 5-FU-triggered cell damage. Moreover, the FITOPROT+5-FU association showed higher cytotoxic effects on SSC-4 cancer cells. Flow cytometry and/or fluorescence microscopy analysis showed FITOPROT was able to significantly reduce ROS generation and prevent mitochondrial changes in HaCaT cells. In addition, it avoided the release of cytochrome c from mitochondria to the cytoplasm in cells exposed to 5-FU, and restored their proliferative activity via Ki-67 expression. Furthermore, FITOPROT regulated 5-FU-induced oxidative stress via Nrf2 involvement. HaCaT cells pretreated/treated with FITOPROT also showed normal expression of TNF-R1 and NF-κB inflammatory proteins and decreased levels of pro-inflammatory cytokines (TNF, IL-1β, IL-6 and IL-8). Moreover, a high-resolution liquid chromatography-mass spectrometry analysis showed the presence of flavonoids rutin, glucoronylated quercetin and dimethylquercetin rutenoside in FITOPROT., Significance: It was showed that FITOPROT, an antioxidant phytochemicals-rich mucoadhesive formulation, exerts chemopreventive effects against 5-FU-triggered toxicity through antioxidant and anti-inflammatory mechanisms and restoration of proliferative capacity in HaCaT cells., (Copyright © 2017. Published by Elsevier Inc.)

The kinetics of a thermostable extracellular acid protease produced by an Aspergillus foetidus strain was investigated at different pH, temperatures and substrate concentrations. The enzyme exhibited maximal activity at pH 5.0 and 55°C, and its irreversible deactivation was well described by first-order kinetics. When temperature was raised from 55 to 70°C, the deactivation rate constant increased from 0.018 to 5.06h(-1), while the half-life decreased from 37.6 to 0.13h. The results of activity collected at different temperatures were then used to estimate, the activation energy of the hydrolysis reaction (E*=19.03kJ/mol) and the standard enthalpy variation of reversible enzyme unfolding (ΔH°U=19.03kJ/mol). The results of residual activity tests carried out in the temperature range 55-70°C allowed estimating the activation energy (E(*)d=314.12kJ/mol), enthalpy (311.27≤(ΔH°d≤311.39kJ/mol), entropy (599.59≤ΔS(*)d≤610.49kJ/mol K) and Gibbs free energy (103.18≤ΔG(*)d≤113.87kJ/mol) of the enzyme irreversible denaturation. These thermodynamic parameters suggest that this new protease is highly thermostable and could be important for industrial applications. To the best of our knowledge, this is the first report on thermodynamic parameters of an acid protease produced by A. foetidus., (Copyright © 2015 Elsevier B.V. All rights reserved.)