erythronic-acid and threonic-acid

The common grass yellow butterfly, Eurema mandarina is a Fabaceae-feeding species, the females of which readily oviposit on Albizia julibrissin and Lespedeza cuneata in mainland Japan. We previously demonstrated that the methanolic leaf extracts of these plants, and their highly polar aqueous fractions strongly elicit female oviposition. Furthermore, the three subfractions obtained by ion-exchange chromatographic separation of the aqueous fraction have been found to be less effective alone, but synergistically stimulate female oviposition when combined. This indicates that female butterflies respond to multiple compounds with different acidity. We have previously identified d-pinitol from the neutral/amphoteric subfractions and glycine betaine from the basic subfractions as oviposition stimulants of E. mandarina. The present study aimed to identify active compounds in the remaining acidic subfractions of A. julibrissin and L. cuneata leaf extracts. GC-MS analyses of trimethylsilyl-derivatized samples revealed the presence of six compounds in the acidic subfractions. In bioassays using these authentic chemicals, erythronic acid (EA) and threonic acid (TA) were moderately active in eliciting oviposition responses in E. mandarina, with their d-isomers showing slightly higher activity than their l-isomers. Female responsiveness differed between d-EA and l-TA, the major isomers of these compounds in plants, with the response to d-EA reaching a plateau at concentrations above 0.005% and that to l-TA peaking at a concentration of 0.01%. The natural concentrations of d-EA and l-TA in fresh A. julibrissin and L. cuneata leaves were sufficient to stimulate oviposition. Furthermore, mixing 0.001% d-EA or 0.001% l-TA, to which females are mostly unresponsive, with 0.1% d-pinitol resulted in a synergistic enhancement of the oviposition response. These findings demonstrate that E. mandarina females utilize both polyhydroxy acids, EA and TA, as chemical cues for oviposition.

Topics: Animals; Butterflies; Female; Inositol; Oviposition; Plant Extracts; Plants

An LC-MS/MS-based bioanalytical method has been developed to measure the concentration of L-threonate at its endogenous level in human plasma. Following isotope dilution and protein precipitation, the samples were acetylated and chromatographed under reversed-phase conditions for baseline separation of the derivatized L-threonate and its stereoisomer D-erythronate. The method was assessed by a fit-for-purpose validation with a calibration range from 100 to 10,000 ng/mL. The intra-run coefficients of variation (CVs) were <3.6% and the inter-run CV was 3.2% for the QC samples at endogenous level. At the lower limit of quantitation, the intra-run CV was 6.1% and the average inaccuracy was -1.4%. This method provides an efficient and reliable quantitation of L-threonate and could be useful to certain biomarker investigators.

Topics: Butyrates; Chromatography, High Pressure Liquid; Humans; Linear Models; Reproducibility of Results; Sensitivity and Specificity; Tandem Mass Spectrometry

Using a large-scale "genomic enzymology" approach, we (i) assigned novel ATP-dependent four-carbon acid sugar kinase functions to members of the DUF1537 protein family (domain of unknown function; Pfam families PF07005 and PF17042) and (ii) discovered novel catabolic pathways for d-threonate, l-threonate, and d-erythronate. The experimentally determined ligand specificities of several solute binding proteins (SBPs) for TRAP (tripartite ATP-independent permease) transporters for four-carbon acids, including d-erythronate and l-erythronate, were used to constrain the substrates for the catabolic pathways that degrade the SBP ligands to intermediates in central carbon metabolism. Sequence similarity networks and genome neighborhood networks were used to identify the enzyme components of the pathways. Conserved genome neighborhoods encoded SBPs as well as permease components of the TRAP transporters, members of the DUF1537 family, and a member of the 4-hydroxy-l-threonine 4-phosphate dehydrogenase (PdxA) oxidative decarboxylase, class II aldolase, or ribulose 1,5-bisphosphate carboxylase/oxygenase, large subunit (RuBisCO) superfamily. Because the characterized substrates of members of the PdxA, class II aldolase, and RuBisCO superfamilies are phosphorylated, we postulated that the members of the DUF1537 family are novel ATP-dependent kinases that participate in catabolic pathways for four-carbon acid sugars. We determined that (i) the DUF1537/PdxA pair participates in a pathway for the conversion of d-threonate to dihydroxyacetone phosphate and CO2 and (ii) the DUF1537/class II aldolase pair participates in pathways for the conversion of d-erythronate and l-threonate (epimers at carbon-3) to dihydroxyacetone phosphate and CO2 The physiological importance of these pathways was demonstrated in vivo by phenotypic and genetic analyses.

Topics: Bacteria; Bacterial Proteins; Butyrates; Fructose-Bisphosphate Aldolase; Oxidoreductases; Phosphates; Protein Domains; Protein Kinases

The influences of various factors in 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation on delignification, lignin aromatic ring and side chain structures of thermomechanical pulp (TMP) were investigated. The results indicate neither TEMPO nor NaBr alone can provoke changes in lignin content or lignin structure under weakly alkaline conditions. However, NaClO and NaClO-NaBr were able to remove lignin effectively, causing remarkable changes in lignin structure. Delignification was promoted when TEMPO was used with NaBr and NaClO. In contrast to NaClO alone, an additional 15% lignin was removed when TEMPO-mediated oxidation system was used, but it did not induce further changes on lignin structure. Increased doses of oxidizing agent and reaction time also improved the oxidation of cellulose and delignification, but they did not have a significant impact on lignin aromatic and side chain structures.

Topics: Butyrates; Cyclic N-Oxides; Lignin; Mechanical Phenomena; Nitrobenzenes; Oxidation-Reduction; Ozone; Paper; Temperature

A multinuclear NMR study of the interaction between phenylboronic acid (PBA) and sialic acid (Neu5 Ac) has been performed. The latter compound is known to be overexpressed on the cell surface of tumor cells. The results of this investigation suggest that the binding of PBA to sialic acid is pH dependent. 17O NMR experiments with glycolic acid as the model compound prove that an interaction at the alpha-hydroxycarboxylate occurs at pH < 9, while a study with threonic and erythronic acids shows that the PBA group interacts selectively with the vicinal diol functions at higher pH. Similarly, Neu5 Ac binds PBA through its alpha-hydroxycarboxylate at low pH (< 9) and through its glycerol side chain at higher pH values. The conditional stability constant of the phenylboronate ester at pH 7.4 is 11.4. On cell surfaces, sialic acid is connected to the neighboring sugar unit through the 2-hydroxy group. To mimic this the 2-alpha-O-methyl derivative of Neu5 Ac was included in this study. The erythro configuration of the hydroxy substituents prevents stable-complex formation at positions C7 and C8 and, consequently, the strongest interaction is observed at positions C8 and C9, leading to a five-membered 2-boron-1,3-dioxalate. In addition, a relatively small amount of the C7-C9 six-membered complex was observed. Molecular modeling studies confirm that the C8-C9 boronate complex has the lowest energy.

Topics: Boronic Acids; Butyrates; Esters; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Molecular Structure; N-Acetylneuraminic Acid

When the cultural atmosphere of the white-rot basidiomycete, Phanerochaete chrysosporium, was changed from air to 100% oxygen, the lyophilized mycelial weight increased and thickening of extracellular glucan layer was observed in 2-3 days. To better understand the oxygen-stress responsive mechanism of P. chrysosporium, the metabolomic differential display analysis was performed using metabolites isolated from fungal cells grown under either air or 100% O(2) atmosphere. In the GC-MS total ion chromatogram of methanol-extracts from fungal cells, at least 183 peaks were detected and 53 compounds were identified. Among them, veratryl alcohol (VA), threonate, and erythronate were identified as oxygen-stress responsive metabolites. The intracellular concentration of VA increased dramatically within 1 h after an oxygen purge, indicating that VA production is sensitive to the oxygen stress in P. chrysosporium.

Topics: Air; Benzyl Alcohols; Biomass; Butyrates; Gas Chromatography-Mass Spectrometry; Glucans; Mycelium; Oxidative Stress; Oxygen; Phanerochaete

Sugars in the aqueous humour of the eye serve both as a source of nutrients to the lens and other anterior ocular tissues, and potentially as an indicator of waste products from these tissues. In this work we intended to measure the levels of sugars in human blood and aqueous humour from cataract patients with and without diabetes. After initial results we decided to identify an unknown sugar component.. Sugars were measured by hplc. The unknown sugar peak was identified by gas chromatography/mass spectrometry. Very little fructose and sorbitol were found. Glucose levels were higher in both blood and aqueous from diabetic patients. During these analyses we found a major component that did not correspond to any sugar reported previously in aqueous humour. This was identified as a mixture of threonic and erythronic acids.. Glucose levels increase in human aqueous humour in diabetes without markedly raised levels of sorbitol or fructose. Erythronic and threonic acids are normal components of aqueous humour and blood. They may be derived from glycated proteins or from degradation of ascorbic acid.

Topics: Aged; Aged, 80 and over; Aqueous Humor; Butyrates; Carbohydrate Metabolism; Chromatography, High Pressure Liquid; Diabetes Mellitus; Female; Gas Chromatography-Mass Spectrometry; Humans; Male; Reference Values