Donors, glycosyl groups

Transferases catalyze transfer of groups such as methyl or glycosyl groups from a donor molecule to an acceptor molecule. 

As already observed for azidoglucose-derived donors, glycosylations with azidolactose-derived donors (21f-a-21j-a, Table XXIV) also exhibited high reactivity and/ selectivity (92,114,115,154,161,162). With these results in hand, excellent preconditions for successful syntheses of the Le and Ley antigens have been presented (164,165). Representative examples for the decisive glycoside-bond formations are compiled in Table XXV. Comparison of the results of V-phthaloyl protection and of the azido group does not exhibit advantages for the use of TV-phthaloyl derivatives. 

The classic enzyme commission (EC) classification for GTs is on the basis of their donor and acceptor specihcity as well as the product formed. Currently, 295 entries are in this database (http //www.chem.qmul.ac.uk/iubmb/). The distinction between these enzymes is noted by their ability to catalyze the transfer of hexoses (EC 2.4.l.y, hexosyltransferases), pentoses (EC 2.4.2.y, pentosyltransferases), or other glycosyl groups (2.4.99.y, sialyltransferases). This classification is restricted to enzymes that are fully characterized, and it can be problematic for enzymes that act on several distinct acceptors but at different rates. It also does not take into account the origin of the enzyme or its three-dimensional stmcture. 

Transferases are enzymes that transfer a chemical group, such as a methyl or glycosyl group, from one compound (the donor) to another compound (the acceptor). In many cases, the donor is a cofactor that carries the group to be transferred. A relatively large number of transferases is known (about 720), of which about 90 are available. 

Specificity For the glycosyl donor, glycosyl acceptor and the nucleotide leaving group For the glycosyl donor and sometimes partially for the glycosyl acceptor... 

---