Leloir-type glycosyltransferases

In this context, the use of enzymes has emerged as a practical alternative to chemical synthesis [6-13]. Several examples have been reported that are based on the use of Leloir type-glycosyltransferases, which are mostly membrane-associated and act on nucleotide-activated sugars as donor substrates. However, the use of these enzymes in vitro still remains limited by the difficulty of enzyme purification and by their need for expensive sugar-nucleotides [6]. Re-engineering of microbial cells producing these proteins appears to be promising for the synthesis of specific carbohydrate stmctures [14]. 

Leloir-type glycosyltransferases are typically membrane bound. In this regard, the use of immobilized enzyme systems [38] may advantageously create enhanced stability one ready method is the use of affinity supports [39, 40]. In addition, the membrane bound nature of Gly-Ts may require the removal of an enzyme s membrane-binding domain to ensure solubility. 

Highly selective enzymatic synthesis using glycosyltransferases (GTFs), an approach restricted by the limited availability of Leloir-type enzymes, and expensive nucleotide-activated substrates... 

It follows from the above that, if highly specific oligosaccharides need to be synthesized, glycosyltransferases [21] of the Leloir type [22] should be the enzymes of choice. These enzymes connect sugars via the activated nucleotide components with high stereo- and regioselectivity. They are substrate-specific, but, in vitro, with solubilized enzymes, it becomes possible to transfer modified donors to modified acceptors and thus broaden the scope of the synthetic applicability. 

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