The identification and molecular characterization of the first archaeal bifunctional exo-ß-glucosidase/N-acetyl-ß-glucosaminidase demonstrate that family GH116 is made of three functionally distinct subfamilies.

BACKGROUND: ß-N-acetylhexosaminidases, which are involved in a variety of biological processes including energy metabolism, cell proliferation, signal transduction and in pathogen-related inflammation and autoimmune diseases, are widely distributed in Bacteria and Eukaryotes, but only few examples have been found in Archaea so far. However, N-acetylgluco- and galactosamine are commonly found in the extracellular storage polymers and in the glycans decorating abundantly expressed glycoproteins from different Crenarchaeota Sulfolobus sp., suggesting that ß-N-acetylglucosaminidase activities could be involved in the modification/recycling of these cellular components. METHODS: A thermophilic ß-N-acetylglucosaminidase was purified from cellular extracts of S. solfataricus, strain P2, identified by mass spectrometry, and cloned and expressed in E. coli. Glycosidase assays on different strains of S. solfataricus, steady state kinetic constants, substrate specificity analysis, and the sensitivity to two inhibitors of the recombinant enzyme were also reported. RESULTS: A new ß-N-acetylglucosaminidase from S. solfataricus was unequivocally identified as the product of gene sso3039. The detailed enzymatic characterization demonstrates that this enzyme is a bifunctional ß-glucosidase/ß-N-acetylglucosaminidase belonging to family GH116 of the carbohydrate active enzyme (CAZy) classification. CONCLUSIONS: This study allowed us to propose that family GH116 is composed of three subfamilies, which show distinct substrate specificities and inhibitor sensitivities. GENERAL SIGNIFICANCE: The characterization of SSO3039 allows, for the first time in Archaea, the identification of an enzyme involved in the metabolism ß-N-acetylhexosaminide, an essential component of glycoproteins in this domain of life, and substantially increases our knowledge on the functional role and phylogenetic relationships amongst the GH116 CAZy family members.

Improved production of reducing sugars from rice husk and rice straw using bacterial cellulase and xylanase activated with hydroxyapatite nanoparticles.

Purified bacterial cellulase and xylanase were activated in the presence of calcium hydroxyapatite nanoparticles (NP) with concomitant increase in thermostability about 35% increment in production of d-xylose and reducing sugars from rice husk and rice straw was obtained at 80°C by the sequential treatment of xylanase and cellulase enzymes in the presence of NP compared to the untreated enzyme sets. Our findings suggested that if the rice husk and the rice straw samples were pre-treated with xylanase prior to treatment with cellulase, the percentage increase of reducing sugar per 100g of substrate (starting material) was enhanced by about 29% and 41%, respectively. These findings can be utilized for the extraction of reducing sugars from cellulose and xylan containing waste material. The purely enzymatic extraction procedure can be substituted for the harsh and bio-adverse chemical methods.