arabinosyltransferases

Arabinosyltransferases are glycosyltransferases that catalyze the transfer of arabinose residues from activated sugar donors to acceptor molecules. They contribute to the biosynthesis and modification of arabinose-containing polysaccharides and glycoconjugates found in the cell walls and extracellular matrices of bacteria and plants. Donors used by these enzymes include decaprenylphosphoryl-D-arabinose in many bacterial systems and, in some contexts, UDP-arabinose. Many arabinosyltransferases are membrane-associated, reflecting their action on lipid-linked donors at the cytoplasmic membrane.

In bacteria, arabinan synthesis is a key aspect of cell wall architecture in mycobacteria and related species. Enzymes such as EmbA, EmbB, and EmbC participate in forming the arabinan branches of arabinogalactan, a component linked to the galactan core of the cell wall. Other arabinosyltransferases, including AftA, AftB, and AftC, contribute to additional modifications of the arabinan network. Inhibitors of these enzymes, notably ethambutol, disrupt mycobacterial cell wall assembly and have clinical utility as antitubercular agents.

In plants, arabinosyltransferases modify cell wall polysaccharides and glycoproteins by adding arabinose residues to xylose-containing backbones and to hydroxyproline-rich proteins. These activities influence cell wall properties such as porosity, rigidity, and signaling, and involve diverse glycosyltransferase families.

Overall, arabinosyltransferases are essential for constructing arabinose-containing macromolecules, with relevance to microbial pathogenicity, plant biology, and biotechnological applications. Research continues to elucidate their substrates, donor specificities, regulatory mechanisms, and structural features.