1.Tautomers of Gas-Phase Erythrose and Their Interconversion Reactions: Insights from High-Level ab Initio Study.
Szczepaniak M1, Moc J1. J Phys Chem A. 2015 Nov 5;119(44):10946-58. doi: 10.1021/acs.jpca.5b07720. Epub 2015 Oct 22.
D-Erythrose is a C4 monosaccharide with a biological and potential astrobiological relevance. We have investigated low-energy structures of d-erythrose and their interconversion in the gas phase with the highest-level calculations up-to-date. We have identified a number of structurally distinct furanose and open-chain isomers and predicted α ↔ α and β ↔ β furanose interconversion pathways involving the O-H rotamers. We have estimated relative Gibbs free energies of the erythrose species based on the CCSD(T)/aug-cc-pVTZ electronic energies and MP2/aug-cc-pVTZ vibrational frequencies. By using natural bond orbital theory we have also quantified a stabilization of erythrose conformers and interconversion transition states by intramolecular H-bonds.
2.Transcript Quantification of Genes Involved in Steviol Glycoside Biosynthesis in Stevia rebaudiana Bertoni by Real-Time Polymerase Chain Reaction (RT-PCR).
Modi A1, Kumar N2, Narayanan S3. Methods Mol Biol. 2016;1391:289-301. doi: 10.1007/978-1-4939-3332-7_20.
Stevia (Stevia rebaudiana Bertoni) is a medicinal plant having sweet, diterpenoid glycosides known as steviol glycosides which are 200-300 times sweeter than sucrose (0.4 % solution). They are synthesized mainly in the leaves via plastid localized 2-C-methyl-D-erythrose-4-phosphate pathway (MEP pathway). Fifteen genes are involved in the formation of these glycosides. In the present protocol, a method for the quantification of transcripts of these genes is shown. The work involves RNA extraction and cDNA preparation, and therefore, procedures for the confirmation of DNA-free cDNA preparation have also been illustrated. Moreover, details of plant treatments are not mentioned as this protocol may apply to relative gene expression profile in any medicinal plant with any treatment. The treatments are numbered as T0 (Control), T1, T2, T3, and T4.
3.Regulation of primary metabolic pathways in oyster mushroom mycelia induced by blue light stimulation: accumulation of shikimic acid.
Kojima M1, Kimura N1, Miura R1. Sci Rep. 2015 Feb 27;5:8630. doi: 10.1038/srep08630.
Shikimic acid is a key intermediate in the aromatic amino acid pathway as well as an important starting material for the synthesis of Tamiflu, a potent and selective inhibitor of the neuraminidase enzyme of influenza viruses A and B. Here we report that in oyster mushroom (Pleurotus ostreatus) mycelia cultivated in the dark, stimulation with blue light-emitting diodes induces the accumulation of shikimic acid. An integrated analysis of primary metabolites, gene expression and protein expression suggests that the accumulation of shikimic acid caused by blue light stimulation is due to an increase in 3-deoxy-D-arabinoheptulosonate 7-phosphate synthase (DAHPS, EC22.214.171.124), the rate-determining enzyme in the shikimic acid pathway, as well as phosphofructokinase (PFK, EC126.96.36.199) and glucose-6-phosphate dehydrogenase (G6PD, EC188.8.131.52), the rate-determining enzymes in the glycolysis and pentose phosphate pathways, respectively. This stimulation results in increased levels of phosphoenolpyruvic acid (PEP) and erythrose-4-phosphate (E4P), the starting materials of shikimic acid biosynthesis.
4.Theory of the milieu dependent isomerisation dynamics of reducing sugars applied to d-erythrose.
Kaufmann M1, Mügge C2, Kroh LW3. Carbohydr Res. 2015 Dec 11;418:89-97. doi: 10.1016/j.carres.2015.10.010. Epub 2015 Oct 30.
Quantitative (1)H selective saturation transfer NMR spectroscopy ((1)H SST qNMR) was used to fully describe the milieu dependent dynamics of the isomeric system of d-erythrose. Thermodynamic activation parameters are calculated for acidic as well as for basic catalysis combining McConnell's modified Bloch equations for the chemical exchange solved for the constraint of saturating the non-hydrated acyclic isomer, the Eyring equation and Hudson's equation for pH dependent catalysis. A detailed mathematical examination describing the milieu dependent dynamics of sugar isomerisation is provided. Thermodynamic data show evidence that photo-catalysed sugar isomerisation as well as degradation has to be considered. Approximations describing the pH and temperature dependence of thermodynamic activation parameters are derived that indicate the possibility of photo-affecting equilibrium constants. Moreover, the results show that isomerisation dynamics are closely related to degradation kinetics and that sugars' reactivities are altered by the concentration of acyclic carbonyl isomer and the sum of its ring closing rate constants.