Donor-Substrate Specificity of Galactosyltransferases

Donor modifications are of great interest in glycosyltransferase-catalyzed reactions. Information about the donor substrate binding site can lead to better understanding of the topography of the active center of the enzyme and of the mechanism involved in the reaction. For the preparative chemist. 

The enzyme recognizes modified donors such as uridine diphosphate 2-deoxygalactose (UDP-2-d-Gal). The starting material 2-deoxyglucose-6-phos-phate, is formed with hexokinase from 2-d-Glc and ATP, which in turn can be regenerated from PEP with pyruvate kinase, and this is transformed into 2-deoxyglucose-1 -phosphate. 

New sources of biocatalysts such as bovine al-3-galactosyltransferase produced by the baculovirus expression system are available and extend the vast field of enzymatic galactosylation. The enzyme transfers galactose with an a-linkage to the 3-position of the Gal residue in Fucal-2Gal 3l-OR [39]. 

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