Transglycosylasen

Transglycosylasen (transglycosylases) are enzymes that catalyze the transfer of a glycosyl residue from a donor to an acceptor molecule, forming a new glycosidic bond. In contrast to hydrolysis, where water acts as the acceptor, transglycosylation products are oligosaccharides or polysaccharides that are extended or rearranged. Transglycosylases can be specialized glycoside transferases that do not release a glycosyl-enzyme intermediate in the same way as hydrolysis, or glycoside hydrolases whose catalytic action shifts toward transfer under certain conditions.

Biological roles: A prominent function is in bacterial cell wall biosynthesis, where transglycosylases polymerize glycan chains of peptidoglycan by transferring disaccharide units from lipid II to a growing strand. This activity is carried by transglycosylase domains of penicillin-binding proteins and by SEDS family proteins such as RodA and FtsW, which work with PBPs. Transglycosylation is also observed in glycoside hydrolases under high substrate concentration, enabling synthesis of defined oligosaccharides or modification of polysaccharides in vitro or in vivo.

Mechanism and features: Most transglycosylases operate via a glycosyl donor and an acceptor, with water as a poor acceptor under favorable conditions; the outcome depends on enzyme family and substrate geometry. In bacteria, moenomycin-like compounds inhibit transglycosylase activity, while beta-lactam antibiotics target transpeptidases rather than transglycosylases.

Applications: Enzymatic transglycosylation is exploited to synthesize defined oligosaccharides, remodel polysaccharides, and study cell wall assembly; understanding these enzymes informs antibiotic development and industrial biocatalysis.