Glyoxalase-based toolbox for the enantioselective synthesis of α-hydroxy carboxylic acids.

We report highly enantioselective synthesis of L-α-hydroxy carboxylic acids (L-αHCAs) via enzymatic intramolecular Cannizzaro reaction of (hetero)aryl glyoxals in the presence of glutathione-independent human glyoxalase DJ-1. Combined with the optimized synthesis of D-αHCAs using glyoxalases I and II, this approach offers a general, scalable and operationally simple access to both enantiomers of α-hydroxy acids in moderate to excellent yields with uniformly high enantioselectivity.

A continuous spectrophotometric assay for glutathione-independent glyoxalases.

We developed a novel continuous assay to quantitatively characterize the catalytic activity of type III methylglyoxalases, a family of enzymes that detoxify methylglyoxal. This assay is based on spectrophotometric detection of hemithioacetal which forms in the reversible reaction of methylglyoxal with dithiothreitol. Due to rapid interconversion between hemithioacetal and methylglyoxal and the known equilibrium constant, hemithioacetal can be quantified spectrophotometrically at 286 nm and used as a reporter for methylglyoxal. When the concentration of methylglyoxal decreases due to catalytic conversion by methylglyoxalases, the concentration of hemithioacetal concomitantly decreases due to its spontaneous decomposition driven by the shift in equilibrium position. Therefore, the rate of total methylglyoxal consumption is the sum of the rate of hemithioacetal decomposition determined spectrophotometrically and the rate of change of methylglyoxal calculated from known concentrations of hemithioacetal. Varying concentrations of dithiothreitol and methylglyoxal creates a broad range of free methylglyoxal in solution that is crucial for the reliable determination of Michaelis constants. We demonstrate the utility of this assay using several recombinant glyoxalases for which kinetic parameters have been determined. This cost-effective and simple assay offers advantages over the existing discontinuous methods and will be useful for quantitative characterization of catalytic activities of type III methylglyoxalases.

Cetyltrimethylammonium Bromide (CTAB)-Loaded SiO2-Ag Mesoporous Nanocomposite as an Efficient Antibacterial Agent.

To date, Ag-based nanomaterials have demonstrated a high potential to overcome antibiotic resistance issues. However, bare Ag nanomaterials are prone to agglomeration in the biological environment, which results in a loss of antibacterial activity over time. Furthermore, it is still challenging to collect small-sized Ag nanomaterials right after the synthesis process. In this study, spherical-shaped Ag nanoparticles (NPs) (~6-10 nm) were attached on the surface of cetyltrimethylammonium bromide (CTAB)-loaded mesoporous silica nanoparticles (MSNs) (~100-110 nm). Antibacterial activity tests suggested that the obtained nanocomposite can be used as a highly efficient antibacterial agent against both Gram-negative and Gram-positive bacterial strains. The minimum inhibitory concentration (MIC) recalculated to pure Ag weight in nanocomposite was found to be ~1.84 µg/mL (for Escherichia coli) and ~0.92 µg/mL (for Staphylococcus aureus)-significantly smaller compared to values reported to date. The improved antibacterial activity of the prepared nanocomposite can be attributed to the even distribution of non-aggregated Ag NPs per volume unit and the presence of CTAB in the nanocomposite pores.