Cloning,expression and characterization of the esterase estUT1 from Ureibacillus thermosphaericus which belongs to a new lipase family XVIII

A new esterase gene from thermophilic bacteria Ureibacillus thermosphaericus was cloned into the pET32b vector and expressed in Escherichia coli BL21(DE3). Alignment of the estUT1 amino acid sequence revealed the presence of a novel canonical pentapeptide (GVSLG) and 41–47% identity to the closest family of the bacterial lipases XIII. Thus the esterase estUT1 from U. thermosphaericus was assigned as a member of the novel family XVIII. It also showed a strong activity toward short-chain esters (C2–C8), with the highest activity for C2. When p-nitrophenyl butyrate is used as a substrate, the temperature and pH optimum of the enzyme were 70–80 °C and 8.0, respectively. EstUT1 showed high thermostability and 68.9 ± 2.5% residual activity after incubation at 70 °C for 6 h. Homology modeling of the enzyme structure showed the presence of a putative catalytic triad Ser93, Asp192, and His222. The activity of estUT1 was inhibited by PMSF, suggesting that the serine residue is involved in the catalytic activity of the enzyme. The purified enzyme exhibited high stability in organic solvents. EstUT1 retained 85.8 ± 2.4% residual activity in 30% methanol at 50 °C for 6 h. Stability at high temperature and tolerance to organic solvents make estUT1 a promising enzyme for biotechnology application.

     

Spontaneous Resolution and Super-coiling in Xerogels of the Products of Photo-Induced Formose Reaction

This work addresses the supramolecular self-organization in the xerogels of formose reaction products. The UV-induced formose reaction was held in over-saturated formaldehyde solutions at 70^°C without a catalyst. The solutions of the obtained carbohydrates were dried on a glass slide, and the obtained xerogels demonstrated a prominent optical activity, while the initial solutions were optically inactive. The xerogels contained highly elongated crystalline elements of a helical structure as well as the isometric ones. Thus xerogel formation was accompanied by a spontaneous resolution of enantiomers and separation of different-shaped supramolecular structures. The thick helices were twisted of thinner ones, while the latter were twisted of elementary structures having a diameter much smaller than 400 nm. Similar structural hierarchy is typical of biological macromolecules (DNA, proteins, and cellulose). Summarizing the obtained results, we proposed a hypothetical mechanism explaining the amplification of the initial enantiomeric excess, as well as chiral and chemical purification of the substances which were essential for the evolution of Life to start.

     

Deuterium Oxide Enhances <Emphasis Type="Italic">Escherichia coli</Emphasis> SOS Response Induced by Genotoxicants

It has been demonstrated that deuterium oxide enhances the SOS response of Escherichia coli cells induced by chemical genotoxicants and mutagens. This demonstrates that the heavy nonradioactive hydrogen isotope deuterium can be considered to be a comutagen.     

Plausible prebiotic synthesis of aldopentoses from simple substrates, glycolaldehyde and formaldehyde

Possible ways of abiotic catalytic synthesis of biologically significant aldopentoses (ribose, xylose, arabinose, lyxose) from elementary substrates, i.e., formaldehyde (FA) and glycolaldehyde (GA) in aqueous solutions are discussed. Conditions in which the process of synthesis of pentoses yields up to 65% relative to the initial concentration of GA: homogeneous borate catalyst NaOH + H₃BO₃, pH 9, [GA]₀ 5 mM, [FA]₀ 50–100 mM have been found.