Image courtesy of K. Michalska, et al. “GH1-family 6-P-ß-glucosidases from human microbiome lactic acid bacteria.” Acta Crystallogr. D D69, 451–463 (2013).
Overall structure of 6-P-β-glucosidase and its comparison with 6-P-β-galactosidase. Using X-ray crystallography techniques, researchers obtained the high-resolution crystal structures of the glucosidase enzyme from lactic acid bacteria, an important catalyst in cellulose deconstruction.
A key step in the production of biofuels from biomass is hydrolytic breakdown of cellulose, a major component of all plants, into simple, fermentable sugars. Many natural systems carry out this deconstruction, and much research is devoted to finding highly efficient enzyme systems that are candidates for inclusion in biofuel production processes. A new study of a subfamily of glucosidase enzymes (6-P-β-glucosidases), which are critical to efficient hydrolysis of cellulose, uses x-ray crystallography to determine the structures of these enzymes and how they bind to cellulose molecules.
These new findings will help scientists studying the design of efficient enzyme systems for biofuel production and also will have implications for human health.
Researchers isolated the glucosidase enzymes from two bacteria commonly found in the digestive tracts of many mammals, including humans: Lactobacillus plantarum and Streptococcus mutans. They obtained structures of the enzymes both alone and bound to key molecules involved in cellulose breakdown using Structural Biology Center stations at Argonne National Laboratory’s Advanced Photon Source. Different bacteria show different P-β-glucosidase and P-β-galactosidase activities. The structures and functional studies enabled the scientists to define structural features shared by glucosidases and galactosidases and those that are unique to the 6-P-β-glucosidases subfamily. Both enzymes show hydrolytic activity against 6’-P-β-glucosides but exhibit surprisingly different kinetic properties and affinities for substrates. Considering the conservation of the overall structures and active sites of various 6-P-β-glucosidases, the differences at their ligand binding subsites and the entrance to the active site are the likely determinants of their substrate specificities.
Midwest Center for Structural Genomics, Biosciences Division, Argonne National Laboratory
This research was funded in part by a grant from the National Institutes of Health (GM094585) and by the DOE Office of Science Biological and Environmental Research program under Contract DE-AC02-06CH11357
Michalska, K., et al. “GH1-family 6-P-ß-glucosidases from human microbiome lactic acid bacteria.” Acta Crystallogr. D D69, 451–463 (2013). [DOI: 10.1107/5090744491].
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