Cloning, sequencing, and expression of a beta-amylase gene from Bacillus cereus var. mycoides and characterization of its products

CBM20CP, a novel functional protein of starch metabolism in green algae

Ostreococcus tauri is a picoalga that contains a small and compact genome, which resembles that of higher plants in the multiplicity of enzymes involved in starch synthesis (ADP-glucose pyrophosphorylase, ADPGlc PPase; granule bound starch synthase, GBSS; starch synthases, SSI, SSII, SSIII; and starch branching enzyme, SBE, between others), except starch synthase IV (SSIV). Although its genome is fully sequenced, there are still many genes and proteins to which no function was assigned. Here, we identify the OT_ostta06g01880 gene that encodes CBM20CP, a plastidial protein which contains a central carbohydrate binding domain of the CBM20 family, and a coiled coil domain at the C-terminus that lacks catalytic activity. We demonstrate that CBM20CP has the ability to bind starch, amylose and amylopectin with different affinities. Furthermore, this protein interacts with OsttaSSIII-B, increasing its binding to starch granules, its catalytic efficiency and promoting granule growth. The results allow us to postulate a functional role for CBM20CP in starch metabolism in green algae. KEY MESSAGE: CBM20CP, a plastidial protein that has a modular structure but lacks catalytic activity, regulates the synthesis of starch in Ostreococcus tauri.

Fusion of maltooligosaccharide-forming amylases from two origins for the improvement of maltopentaose synthesis

Maltopentaose-forming amylases are promising enzymes for their ability to hydrolyze starch and produce functional maltooligosaccharides. Two maltopentaose-forming amylase genes from Bacillus megaterium (BmMFA) and Saccharophagus degradans (SdMFA) were expressed heterologously and their characteristics were analyzed. BmMFA has substantial thermostability and SdMFA owns superior product specificity. The carbohydrate-binding module of SdMFA was fused with BmMFA and the fused protein showed ideal enzymatic properties and displayed potential for industrial production of maltopentaose. Under the optimized conditions, the final product containing 47.41% maltopentaose was obtained with a conversion rate of 92.67% from starch. This study provides a novel strategy for the directed modification of MFAses through protein fusion approach.

Enhanced Catalysis from Multienzyme Cascades Assembled on a DNA Origami Triangle

Developing reliable methods of constructing cell-free multienzyme biocatalytic systems is a milestone goal of synthetic biology. It would enable overcoming the limitations of current cell-based systems, which suffer from the presence of competing pathways, toxicity, and inefficient access to extracellular reactants and removal of products. DNA nanostructures have been suggested as ideal scaffolds for assembling sequential enzymatic cascades in close enough proximity to potentially allow for exploiting of channeling effects; however, initial demonstrations have provided somewhat contradictory results toward confirming this phenomenon. In this work, a three-enzyme sequential cascade was realized by site-specifically immobilizing DNA-conjugated amylase, maltase, and glucokinase on a self-assembled DNA origami triangle. The kinetics of seven different enzyme configurations were evaluated experimentally and compared to simulations of optimized activity. A 30-fold increase in the pathway's kinetic activity was observed for enzymes assembled to the DNA. Detailed kinetic analysis suggests that this catalytic enhancement originated from increased enzyme stability and a localized DNA surface affinity or hydration layer effect and not from a directed enzyme-to-enzyme channeling mechanism. Nevertheless, the approach used to construct this pathway still shows promise toward improving other more elaborate multienzymatic cascades and could potentially allow for the custom synthesis of complex (bio)molecules that cannot be realized with conventional organic chemistry approaches.

Extraction and purification of beta-amylase from stems of Abrus precatorius by three phase partitioning

The stems of Abrus precatorius were used to extract a beta-amylase enriched fraction. A three phase partitioning method and a Doehlert design with 3 variables (ratio of crude extract/t-butanol, the ammonium sulphate saturation and pH) were used. The data was fitted in a second-order polynomial model and the parameters were optimized to enrich beta-amylase. Experimental responses for the modulation were recovery of activity and the purification factor. The optimal conditions were: a ratio of crude extract/t-butanol of 0.87 (v/v), saturation in ammonium sulphate of 49.46% (w/v) and a pH of 5.2. An activity recovery of 156.2% and a purification factor of 10.17 were found. The enriched enzyme was identified as a beta-amylase and its molecular weight was 60.1kDa. Km and Vmax values were 79.37mg/ml and 5.13U/ml, respectively and the highest activity was registered at a temperature of 70°C and a pH between 6 and 6.5. A significant stabilization of the beta-amylase was observed up to 65°C.

Beta-amylases from various fungal strains. A review

An overview presentation is made on the current global status of fungal beta3-amylases, their characteristics and applications in various industries. Among the few available report on beta-amylase producing fungal strains, many showed a preference for a cultivation temperature of 28 degrees C, acidic pH and soluble starch as an inducer of enzyme synthesis. In some fungal strains, alpha-amylase and alpha-glucosidases were found to be present as major contaminating enzymes. Although the existence of a few starch digesting and raw starch adsorbing fungal strains were reported, detailed study on molecular biology of corresponding fungal genes was not available.