Effects of the PT region of EngD and HLD of CbpA on solubility, catalytic activity and purification characteristics of EngD-CBDCbpA fusions from Clostridium cellulovorans

Recombinant CBM-fusion technology - Applications overview

Carbohydrate-binding modules (CBMs) are small components of several enzymes, which present an independent fold and function, and specific carbohydrate-binding activity. Their major function is to bind the enzyme to the substrate enhancing its catalytic activity, especially in the case of insoluble substrates. The immense diversity of CBMs, together with their unique properties, has long raised their attention for many biotechnological applications. Recombinant DNA technology has been used for cloning and characterizing new CBMs. In addition, it has been employed to improve the purity and availability of many CBMs, but mainly, to construct bi-functional CBM-fused proteins for specific applications. This review presents a comprehensive summary of the uses of CBMs recombinantly produced from heterologous organisms, or by the original host, along with the latest advances. Emphasis is given particularly to the applications of recombinant CBM-fusions in: (a) modification of fibers, (b) production, purification and immobilization of recombinant proteins, (c) functionalization of biomaterials and (d) development of microarrays and probes.

Enhancement of Streptomyces transglutaminase activity and pro-peptide cleavage efficiency by introducing linker peptide in the C-terminus of the pro-peptide

Streptomyces transglutaminase (TGase) has been widely used in food, pharmaceutical and textile industries. Streptomyces TGase is naturally synthesized as zymogen (pro-TGase), which is then processed to produce active enzyme by removing its N-terminal pro-peptide. Although the pro-peptide is essential for TGase folding and secretion, few studies have been reported on improving the properties of TGase by pro-peptide engineering. In this study, we developed a new approach to improve the properties of TGase based on pro-peptide engineering. When the α-helix37G−42S in pro-peptide was substituted with three glycines and three alanines respectively, the mutants exhibited higher specific activity and the efficiency of pro-peptide cleavage was enhanced. To further improve the properties of TGase, relevant mutations were constructed by introducing linker peptides in the C-terminus of the pro-peptide. Mutants with GS (GGGGS) and PT (PTPPTTPT) linker peptide exhibited 1.28 fold and 1.5 fold higher specific activity than the wild-type enzyme, respectively. This new method could be used to improve the properties of TGase by pro-peptide modification, which is a promising technology for creating unique TGase with various beneficial properties.

Efficiency and stability enhancement of cis-epoxysuccinic acid hydrolase by fusion with a carbohydrate binding module and immobilization onto cellulose

Cis-epoxysuccinic acid hydrolase (CESH) is an enzyme that catalyzes cis-epoxysuccinic acid to produce enantiomeric L(+)-tartaric acid. The production of tartaric acid by using CESH would be valuable in the chemical industry because of its high yield and selectivity, but the low stability of CESH hampers its application. To improve the stability of CESH, we fused five different carbohydrate-binding modules (CBMs) to CESH and immobilized the chimeric enzymes on cellulose. The effects of the fusion and immobilization on the activity, kinetics, and stability of CESH were compared. Activity measurements demonstrated that the fusion with CBMs and the immobilization on cellulose increased the pH and temperature adaptability of CESH. The chimeric enzymes showed significantly different enzyme kinetics parameters, among which the immobilized CBM30-CESH exhibited twofold catalytic efficiency compared with the native CESH. The half-life measurements indicated that the stability of the enzyme in its free form was slightly increased by the fusion with CBMs, whereas the immobilization on cellulose significantly increased the stability of the enzyme. The immobilized CBM30-CESH showed the longest half-life, which is more than five times the free native CESH half-life at 30 °C. Therefore, most CBMs can improve enzymatic properties, and CBM30 is the best fusion partner for CESH to improve both its enzymatic efficiency and its stability.

Molecular engineering of the cellulosome complex for affinity and bioenergy applications

The cellulosome complex has evolved to degrade plant cell walls and, as such, combines tenacious binding to cellulose with diverse catalytic activities against amorphous and crystalline cellulose. Cellulolytic microorganisms provide an extensive selection of domains; those with affinity for cellulose, cohesins and their dockerin binding partners that define cellulosome stoichiometry and architecture, and a range of catalytic activities against carbohydrates. These robust domains provide the building blocks for molecular design. This review examines how protein modules derived from the cellulosome have been incorporated into chimaeric proteins to provide biosynthetic tools for research and industry. These applications include affinity tags for protein purification, and non-chemical methods for immobilisation and presentation of recombinant protein domains on cellulosic substrates. Cellulosomal architecture provides a paradigm for design of enzymatic complexes that synergistically combine multiple catalytic subunits to achieve higher specific activity than would be obtained using free enzymes. Multimeric enzymatic complexes may have industrial applications of relevance for an emerging carbon economy. Biocatalysis will lead to more efficient utilisation of renewable carbon-fixing energy sources with the added benefits of reducing chemical waste streams and reliance on petroleum.

Fusion to a pull-down domain: a novel approach of producingTrigonopsis variabilisD-amino acid oxidase as insoluble enzyme aggregates

Insoluble protein particles showing high specific enzyme activity are potentially useful biocatalysts. The commercialized crosslinked enzyme crystals and aggregates have the disadvantage that their preparation requires isolation of the protein before the critical precipitation step. We introduce a novel concept of controlled precipitation in vivo in which the target enzyme is fused to the cellulose-binding domain (CBD) of Clostridium cellulovorans, and expression in Escherichia coli is performed under conditions that induce selective pull down of the folded chimeric protein via intermolecular self-aggregation of the CBD. The case of D-amino acid oxidase from Trigonopsis variabilis shows that upon fusion of the CBD to its N-terminus, the otherwise mainly soluble recombinant enzyme was quantitatively precipitated in protein particles, which displayed 40% of the specific activity of the highly purified oxidase. By contrast, inclusion bodies derived from an enzyme chimera, which harbored a C-terminal peptide tag, showed only little oxidase activity (<or= 10%). The aggregated CBD retained the ability to bind microcrystalline cellulose and flocculated polysaccharide particles upon attachment to them. The cellulose-bound oxidase was stabilized about 36 times against inactivation of the soluble enzyme during conversion of D-methionine and bubble aeration.