Preparative scale enzymatic synthesis of D-sedoheptulose-7-phosphate from β-hydroxypyruvate and D-ribose-5-phosphate

International audienceAn enzymatic method for ready access to D-sedoheptulose-7-phosphate on a preparative scale was developed, based on the irreversible transketolase-catalyzed reaction: β-hydroxypyruvate + D-ribose-5- phosphate → D-sedoheptulose-7-phosphate. D-Sedoheptulose-7-phosphate disodium salt was obtained in 81% overall yield determined using a standard curve obtained by LC/MS/MS

An efficient chemoenzymatic route to dihydroxyacetone phosphate from glycidol for the in situ aldoalse-mediated synthesis of monosaccharides

We report a new two-step procedure that uses inexpensive rac-glycidol to obtain valuable dihydroxyacetone phosphate (DHAP), a building block for the synthesis of monosaccharide analogues

2-Aminobenzothiazole degradation by free and Ca-alginate immobilized cells of Rhodococcus rhodochrous

International audience2-Aminobenzothiazole (ABT) degradation was investigated using free and immobilized systems during photodegradation under solar light in the presence of Fe(III)-nitrilotriacetic acid (FeNTA), biodegradation by Rhodococcus rhodochrous, and during combined conditions. Ca-alginate hydrogel was chosen as a model matrix and some complementary studies were required to characterize this new system. R. rhodochrous metabolism in this type of environment was monitored by NMR spectroscopy. Neither change in intracellular pH values nor in ATP concentrations was observed by in vivo 31P NMR, showing that no metabolic modification occurred between free and immobilized cells. 1H NMR demonstrated that alginate was not used as carbon source by R. rhodochrous. After establishing the pre-treatment protocol by SPE to eliminate solubilised alginate, ABT adsorption on beads and degradation were studied. The same pathways of transformation were observed in suspended and immobilized cell systems. Considering the ABT adsorption phenomenon on alginate beads (8%), the efficiency of the two systems was found to be comparable although the degradation rate was slightly lower with immobilized cells. The most important result was the finding that the positive effect of FeNTA on ABT degradation with immobilized cells was similar to that observed previously with free cells. All these results show that mechanisms observed with free cells can be extrapolated to entrapped cells, i.e. under conditions much closer to those usually encountered in the environment

Chemoenzymatic synthesis of 5-thio-D-xylopyranose.

5-thio-D-xylopyranose, a synthon used for the preparation of drugs with antithrombotic activity, was synthesised by an enzymatic isomerisation from the corresponding ketose, 5-thio-D-xylulofuranose, with glucose isomerase. This compound was obtained by two different chemoenzymatic routes, the key step being the stereospecific formation of a C-C bond, catalysed by transketolase or fructose-1,6-bisphosphate aldolas

Chemoenzymatic synthesis of L-tyrosine derivative for a transketolase assay

We have prepared an l-tyrosine derivative bearing a d-threo ketose moiety by a convenient chemoenzymatic route. This compound is of potential interest for developing stereospecific assays for enzymes catalyzing C–C bond cleavage such as transketolase. We showed in vitro by analytical studies (LC/MS and 31P NMR) that this compound can release l-tyrosine in the presence of wild type TK extract and bovine serum albumin. This assay is the first step towards a mutant TK selection test that could be developed for yeast cells auxotrophic for l-tyrosin

Synthesis of stereochemical probes for new fluorogenic assays for yeast transketolase variants.

For the screening of yeast transketolase (TK) variants with improved or new properties acquired by random mutagenesis, we report on the stereoselective synthesis of fluorogenic substrates as probes for measuring TK activity. Compound 1 (7-(2′,3′,5′-trihydroxy-4′-oxo-pentyl)oxycoumarine), prepared as previously described, [Tetrahedron Lett. 2003, 44, 827–830] enabled us to evaluate wild type TK velocity in a simple, specific and reproducible way. To select TK mutants able to produce d-threo aldoses, we prepared compound 2 (dihydroxy-4-O-(2′-oxo-benzopyran-7′-yl-D-threose) from dimethyl tartrate. Starting from d-ribose, we successfully obtained compound 3 (7′-(2,3,5-trihydroxy-4-oxo-pentyl)oxycoumarine) as a probe for TK mutants able to produce l-erythro ketoses

A tool for predicting the thermal performance of a diesel engine

This paper presents a thermal network model for the simulation of the transient response of diesel engines. The model was adjusted by using experimental data from a completely instrumented engine run under steady-state and transient conditions. Comparisons between measured and predicted material temperatures over a wide range of engine running conditions show a mean error of 7◦C. The model was then used to predict the thermal behavior of a different engine. Model results were checked against oil and coolant temperatures measured during engine warm-up at constant speed and load, and on a New European Driving Cycle. Results show that the model predicts these temperatures with a maximum error of 3◦C.Torregrosa, AJ.; Olmeda González, PC.; Martín Díaz, J.; Romero Piedrahita, CA. (2011). A tool for predicting the thermal performance of a diesel engine. Heat Transfer Engineering. 32(10):891-904. doi:10.1080/01457632.2011.548639S891904321

Pyridoacridines in the 21st Century

This minireview summarizes the work developed during this Century with compounds containing the pyridoacridine scaffold in its different isomeric forms. The isolation of natural products, syntheses, bioactivities, chelation capacity, and other properties of compounds containing this framework are discussed. For reasons of length, only compounds containing a maximum of seven condensed rings have been considered, with a few exceptions

Transketolase catalysed upgrading of l-arabinose: the one-step stereoselective synthesis of l-gluco-heptulose

Conversion of biomass using biocatalysis is likely to become a technology that contributes significantly to the future production of chemical building blocks, materials and transport fuels. Here the synthesis of a value-added chemical from L-arabinose, a major component of the carbohydrates in sugar beet pulp (SBP), in a concise and sustainable manner has been investigated. Biocatalytic conversions using transketolase variants have been developed for the efficient, scalable synthesis of a rare naturally occurring ketoheptose, L-gluco-heptulose, from L-arabinose. New active E. coli TK mutants that readily accept L-arabinose were identified using a versatile colorimetric screening assay and the reaction was performed on a preparative scale