Di-glycosylation is the attachment additional of sugar molecules to sugars which are already attached to a small molecule.
These structures are numerous in nature and include Stevia sweeteners, anthocyanin colorants and saponins. The reason for this prevalence is that physicochemical properties as well as biological activities change with every sugar added. So, with each primary sugar containing multiple glycolysablehydroxy groups the combinatorial space is almost endless.
For example the Stevia sweetener Rebaudioside M (see here) has two primary glucose molecules attached and four secondary glucoses attached to these (see illustration below), with a mixture of 1,2- and 1,3-bonds. This particular Rebaudioside is a better sweetener than all other rebaudiosides tested.
Some UGT enzymes are specifically good at di-glycosylating hydroxy group 2 of the primary sugar, others work on group 3 or group 6, creating 1,2-, 1,3- or 1,6-bonds, respectively. Our GLY platform includes examples of all of these types of enzymes in addition to much know-how in this particular area of small molecule glycosylation.