Advances in the Enzymology of Glycosyltransferases: Catalytic Mechanisms, Structural Diversity and Biotechnological Use

Background: Glycosyltransferases (GTs) are a diverse superfamily of enzymes that catalyze the transfer of sugar moieties from activated donor substrates to acceptor molecules, playing essential roles in the biosynthesis of oligosaccharides, glycoproteins, glycolipids, and natural products. Their activity is central to numerous biological processes, including cell signaling, immune recognition, and protein folding. Ongoing advances in enzymology, structural biology, and synthetic glycobiology have significantly deepened our understanding of GT mechanisms and broadened their applications in biotechnology and therapeutic development. Methods and Results: This review provides a comprehensive overview of the catalytic mechanisms and structural classification of GTs, highlighting both inverting and retaining reaction pathways. Using data from X-ray crystallography, cryo-electron microscopy, and molecular dynamics simulations, we discuss conserved GT folds—GT-A, GT-B, and GT-C—and their implications for substrate specificity and catalytic fidelity. Mutagenesis and kinetic studies have revealed how metal ion coordination, acceptor positioning, and conformational changes influence reaction rates and selectivity. Evolutionary insights demonstrate convergent strategies across kingdoms for sugar transfer, including multifunctionality and domain shuffling. From a biotechnological perspective, GTs have become indispensable tools for the chemoenzymatic synthesis of complex glycans, site-specific protein glycoengineering, and the generation of bioactive glycoconjugates. Engineered GTs with altered donor/acceptor specificity and improved thermostability are enabling novel routes to glycomaterials and therapeutic glycans. Recent innovations in cell-free glycosylation platforms and programmable GT arrays are accelerating their integration into synthetic biology pipelines. Conclusion: Glycosyltransferases represent one of the most structurally and functionally versatile classes of enzymes, with growing importance across biomedical and industrial domains.