The structure of a D-lyxose isomerase from the σB regulon of Bacillus subtilis

Biochemical and Structural Characterisation of a Novel D-Lyxose Isomerase From the Hyperthermophilic Archaeon Thermofilum sp

A novel D-lyxose isomerase has been identified within the genome of a hyperthermophilic archaeon belonging to the Thermofilum species. The enzyme has been cloned and over-expressed in Escherichia coli and biochemically characterised. This enzyme differs from other enzymes of this class in that it is highly specific for the substrate D-lyxose, showing less than 2% activity towards mannose and other substrates reported for lyxose isomerases. This is the most thermoactive and thermostable lyxose isomerase reported to date, showing activity above 95°C and retaining 60% of its activity after 60 min incubation at 80°C. This lyxose isomerase is stable in the presence of 50% (v/v) of solvents ethanol, methanol, acetonitrile and DMSO. The crystal structure of the enzyme has been resolved to 1.4–1.7 A. resolution in the ligand-free form and in complexes with both of the slowly reacting sugar substrates mannose and fructose. This thermophilic lyxose isomerase is stabilised by a disulfide bond between the two monomers of the dimeric enzyme and increased hydrophobicity at the dimer interface. These overall properties of high substrate specificity, thermostability and solvent tolerance make this lyxose isomerase enzyme a good candidate for potential industrial applications.

Identification of a novel recombinant D-lyxose isomerase from Thermoprotei archaeon with high thermostable, weak-acid and nickel ion dependent properties

Recently, production of D-mannose becomes a hotspot owing to it exhibiting many physiological functions on people's health and wide applications in food and pharmaceutical field. The use of biological enzymes to production of D-mannose is of particular receiving considerable concerns due to it possessing many merits over chemical synthesis and plant extraction strategies. D-Lyxose isomerase (D-LIase) plays a pivotal role in preparation of D-mannose from d-fructose through isomerization reaction. Thus, a novel putative D-LIase from thermophiles strain Thermoprotei archaeon which was expressed in E. coli BL21(DE3) was first identified and biochemically characterized. The recombinant D-LIase showed an optimal temperature of 80 and 85 °C and pH of 6.5. It was highly thermostable at 70 °C and 80 °C after incubating for 48 h and 33 h, respectively, with retaining over 50% of the initial activity. A lower concentration of Ni²⁺ (0.5 mM) could greatly increase the activity by 25-fold, which was rare reported in other D-LIases. It was a dimer structure with melting temperature of 88.3 °C. Under the optimal conditions, 15.8 g L^-1 of D-mannose and 33.8 g L^-1 of D-xylulose were produced from 80 g L^-1 of d-fructose and D-lyxose, respectively. This work provided a promising candidate sugar isomerase T. archaeon D-LIase for the production of D-mannose and D-xylulose.

Characterization of a D-lyxose isomerase from Bacillus velezensis and its application for the production of D-mannose and L-ribose

D-Mannose and L-ribose are two important monosaccharides, which have attracted public attention recently because of their great application potentials in food, cosmetic and pharmaceutical industries. Sugar isomerases catalyze the sugar isomerization and therefore can be used as the biocatalysts for production of the high-value sugars from inexpensive sugars. L-arabinose isomerase catalyzes the conversion of L-arabinose to L-ribulose, while D-lyxose isomerase catalyzes L-ribulose and D-fructose to L-ribose and D-mannose, respectively. In this paper, a putative D-LI from Bacillus velezensis (BvLI) was identified, characterized and used to produce D-mannose and L-ribose from D-fructose and L-arabinose, respectively. The recombinant BvLI exhibited a maximum activity at 55 °C and pH 6.5, in the presence of 0.1 mM Co²⁺. Approximately 110.75 g/L D-mannose was obtained from 500 g/L D-fructose in 6 h by the recombinant BvLI, and approximately 105 g/L L-ribose was obtained from 500 g/L L-arabinose in 8 h by the successive biocatalysis of L-arabinose isomerase from Bacillus licheniformis (BlAI) and BvLI.

Production of d-mannose from d-glucose by co-expression of d-glucose isomerase and d-lyxose isomerase in Escherichia coli

BACKGROUND

d-Mannose is not only the epimer of d-glucose at the C-2 position, but also the aldose isomer of d-fructose. Because of its physiological properties and health benefits, d-mannose has attracted public interest. It has been confirmed that d-mannose has broad applications in food, cosmetics, and pharmaceutical industries. According to the Izumoring strategy, d-glucose isomerase (d-GI) and d-lyxose isomerase (d-LI) play important roles in the conversions of d-fructose from d-glucose and of d-mannose from d-fructose respectively. In this study, a one-step enzyme process of d-mannose production from d-glucose has been constructed by co-expression of the d-GI from Acidothermus cellulolyticus and d-LI from Thermosediminibacter oceani in Escherichia coli BL21(DE3) cells.

RESULTS

The co-expression system exhibits maximum activity at pH 6.5 and 65 °C with Co²⁺ supplement. It is relatively thermostable at less than 65 °C. When the reaction reaches equilibrium, the ratio of d-glucose, d-fructose, and d-mannose is approximately 34 : 49.6 : 16.4. By using this co-expression system, about 60.0 g L^-1 d-mannose is obtained from 400 g L^-1 d-glucose in 8 h.

CONCLUSION

This co-expression of d-GI and d-LI system provides a novel and efficient approach for d-mannose production. © 2018 Society of Chemical Industry.

Structural insight into the Clostridium difficile ethanolamine utilisation microcompartment

Bacterial microcompartments form a protective proteinaceous barrier around metabolic enzymes that process unstable or toxic chemical intermediates. The genome of the virulent, multidrug-resistant Clostridium difficile 630 strain contains an operon, eut, encoding a bacterial microcompartment with genes for the breakdown of ethanolamine and its utilisation as a source of reduced nitrogen and carbon. The C. difficile eut operon displays regulatory genetic elements and protein encoding regions in common with homologous loci found in the genomes of other bacteria, including the enteric pathogens Salmonella enterica and Enterococcus faecalis. The crystal structures of two microcompartment shell proteins, CD1908 and CD1918, and an uncharacterised protein with potential enzymatic activity, CD1925, were determined by X-ray crystallography. CD1908 and CD1918 display the same protein fold, though the order of secondary structure elements is permuted in CD1908 and this protein displays an N-terminal β-strand extension. These proteins form hexamers with molecules related by crystallographic and non-crystallographic symmetry. The structure of CD1925 has a cupin β-barrel fold and a putative active site that is distinct from the metal-ion dependent catalytic cupins. Thin-section transmission electron microscopy of Escherichia coli over-expressing eut proteins indicates that CD1918 is capable of self-association into arrays, suggesting an organisational role for CD1918 in the formation of this microcompartment. The work presented provides the basis for further study of the architecture and function of the C. difficile eut microcompartment, its role in metabolism and the wider consequences of intestinal colonisation and virulence in this pathogen.