Glycosyltransferase mechanisms

Since GPEs can use a variety of mechanisms to promote enzymatic glycosylation, the timing of proton transfer could in principle be different. This of course is at least partly due to the wide variety of substrates that GPEs utilize. Current modeling of glycosyltransferase mechanisms by QM-MM methods finds late TSs with relatively... 

The condensation step is catalyzed by the glycosyltransferase SpcF. Further enzyme-catalyzed oxidation is probably needed for the introduction of the hemiketal linkage between cyclitol and sugar units. The SpcY enzyme, which has a similar counterpart, HygY, among the /lyg-cluster encoded proteins (see Section 2.2.4.3.1), is a candidate enzyme for this reaction. SpcY is a member of the radical SAM superfamily of proteins and relatives of SpcY have been found before all in connection with molybdenum-cofactor biosynthesis but to our knowledge no details of the mechanism involved is known for those. 

At least three different glycosyltransferases participate in assembly of the polymeric chain through this mechanism (i) the initiation A-transferase,... 

Another possible regulatory mechanism has been pointed out by Elbein for plant systems. His results implied either that the carrier lipid for different sugars are different polyprenyl phosphates, or that the glycosyltransferases have their own pools of lipid carriers, which do not mix.16 The results, compared to those for other plant and animal systems, suggested that the polyprenyl phosphates are the same for different sugars in each system, thus ruling out the first hypothesis, and reinforcing the concept of different pools.30... 

Iminosugars are naturally occurring polyhydroxylated alkaloids,[5] many of them are potent inhibitors of glycosidases and glycosyltransferases (Figure 19.1) [6]. Because of that they have attracted much interest with respect to potential therapeuhc applications [2, 7]. Furthermore, they are useful probes in fundamental biochemical studies of glycosidases mechanism [8]. 

Breton C, Snajdrova L, Jeanneau C, Koca J, Imberty A. Structures and mechanisms of glycosyltransferases. Glycobiology 2006 16 29-37. 

Lariviere L, Sommer N, Morera S. Structural evidence of a passive base-flipping mechanism for ACT, an unusual GT-B glycosyltransferase. J. Mol. Biol. 2005 352 139-150. 

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