title: Engineered N-acetylhexosamine-active enzymes in glycoscience.
abstract: In recent years, enzymes modifying N-acetylhexosamine substrates have emerged in numerous theoretical studies as well as practical applications from biology, biomedicine, and biotechnology. Advanced enzyme engineering techniques converted them into potent synthetic instruments affording a variety of valuable glycosides.
  
  
  
  This review presents the diversity of engineered enzymes active with N-acetylhexosamine carbohydrates: from popular glycoside hydrolases and glycosyltransferases to less known oxidases, epimerases, kinases, sulfotransferases, and acetylases. Though hydrolases in natura, engineered chitinases, β-N-acetylhexosaminidases, and endo-β-N-acetylglucosaminidases were successfully employed in the synthesis of defined natural and derivatized chitooligomers and in the remodeling of N-glycosylation patterns of therapeutic antibodies. The genes of various N-acetylhexosaminyltransferases were cloned into metabolically engineered microorganisms for producing human milk oligosaccharides, Lewis X structures, and human-like glycoproteins. Moreover, mutant N-acetylhexosamine-active glycosyltransferases were applied, e.g., in the construction of glycomimetics and complex glycostructures, industrial production of low-lactose milk, and metabolic labeling of glycans. In the synthesis of biotechnologically important compounds, several innovative glycoengineered systems are presented for an efficient bioproduction of GlcNAc, UDP-GlcNAc, N-acetylneuraminic acid, and of defined glycosaminoglycans.
  
  
  
  The above examples demonstrate that engineering of N-acetylhexosamine-active enzymes was able to solve complex issues such as synthesis of tailored human-like glycoproteins or industrial-scale production of desired oligosaccharides. Due to the specific catalytic mechanism, mutagenesis of these catalysts was often realized through rational solutions.
  
  
  
  Specific N-acetylhexosamine glycosylation is crucial in biological, biomedical and biotechnological applications and a good understanding of its details opens new possibilities in this fast developing area of glycoscience.
authors.affiliation: Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, CZ 14220 Prague 4, Czech Republic.
authors.forename: Kristýna
authors.initials: K
authors.lastname: Slámová
authors.affiliation: Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, CZ 14220 Prague 4, Czech Republic. Electronic address: bojarova@biomed.cas.cz.
authors.forename: Pavla
authors.initials: P
authors.lastname: Bojarová
mesh_terms: D002384:Catalysis; D006023:Glycoproteins / Q000096:biosynthesis; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006031:Glycosylation; D016695:Glycosyltransferases / Q000378:metabolism*; D006595:Hexosamines / Q000378:metabolism*; D009844:Oligosaccharides / Q000096:biosynthesis; D015202:Protein Engineering; D015238:Sulfotransferases / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D006595:Hexosamines; D009844:Oligosaccharides; D016695:Glycosyltransferases; D015238:Sulfotransferases; D006026:Glycoside Hydrolases
keywords: Chitinase; Glycosynthase; Site-directed mutagenesis; Transglycosidase; Whole-cell engineering; β-N-acetylhexosaminidase