Sialyltransferases characterization

It was apparent, however, that the rat brain sialyltransferases have not been sufficiently characterized for the postulation of a biological role for the sialylation-desialylation cycle. Consequently, we concentrated our efforts to characterizing the general behaviors of the sialyltransferases in their membrane environments in the rat brain. What follows is a summary of our... 

Melkerson-Watson LJ, Sweeley CC. Purification to apparent homogeneity by immunoaffinity chromatography and partial characterization of the GM3 gangUoside-forming enzyme, CMP-sialic acid lactosylceramide alpha 2,3-sialyltransferase (SAT-1), from rat liver Golgi. J. Biol. Chem. 1991 266 4448-4457. 

Preuss U, Gu X, Gu T, Yu RK. Purification and characterization of CMP-N-acetylneuraminic acid lactosylceramide (alpha 2-3) sialyltransferase (GM3-synthase) from rat brain. J. Biol. Chem. 1993 268 26273-26278. 

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. 

Kono M, Takashima S, Liu H, Inoue M, Kojima N, Lee YC, Hamamoto T, Tsuji S. Molecular cloning and functional expression of a fifth-type alpha 2,3-sialyltransferase (mST3Gal V GM3 synthase). Biochem. Biophys. Res. Commun. 1998 253-175. Daniotti JL, Martina JA, Giraudo CG, Zurita AR, Maccioni HJ. GM3 alpha2,8-sialyltransferase (GD3 synthase) protein characterization and sub-golgi location in CHO-Kl cells. J. Neurochem. 2000 74 1711-1720. 

Characterization of a bifunctional bacterial sialyltransferase, Cst-11 cloned from C. jejuni having both a2,3- and a2,8-sialyltransferase activities, has been reported. This sialyltransferase has been used for the synthesis of GD3 oligosaccharides Neu5Aco2,8Neu5Ac(x2,3LacOR and other gangliosides (53, 54). 

The chemical relationship of the seven forms of human liver a-L-fucosidase has been studied by isoelectric focusing of neuraminidase and sialyltransferase-treated preparations of a-L-fucosidase. Neuraminidase treatment leads to a decrease in the activity of the more-acidic forms, and a concomitant increase in the activity of the more-neutral forms. Incubation of the neuraminidase-treated enzyme forms with a radiolabelled CMP-neuraminic acid and sialyl-transferase led to generation of more-acidic forms of the enzyme. The seven isoenzymes were separated by preparative isoelectric focusing and were characterized kinetically and immunochemically. 

Baum, L.G., Derbin, K., Perillo, N.L., Wu, T., Pang, M. and Uittenbogaart, C. Characterization of terminal sialic acid linkages on human thymocytes. Correlation between lectin-binding phenotype and sialyltransferase expression. J. Biol. Chem., 271, 10793-10799 (1996). 

Busam K, Decker K. Ganglioside biosynthesis in rat liver. Characterization of three sialyltransferases. Eur. J. Biochem. 1986 I60 23-30. 

Daniotti JL, Rosales F, V, Kunda P, Nishi T, Maccioni HJ. Cloning, characterization and developmental expression of 2,8 sialyltransferase (GD3 synthase, ST8Sia I) gene in chick brain and retina. Inti J. Dev. Neuroscl 1997 15 767-776. 

Yoshida Y, Kojima N, Tsuji S. Molecular cloning and characterization of a third type of N-glycan 2,8-sialyltransferase from mouse lung. 7. Biochem. (Tokyo) 1995 118 658-664. 

Table 5. Characterization of different glycolipid sialyltransferases using donor CMP-NeuAc.

However, little is known about the expression of Lewis-x and sialyl-Lewis-x blood-group glycolipids with multilactosamine (or poly-lactosamine) chain-bound to ceramide. A novel sialyltransferase, SAT-3 (CMP-NeuAc nLcOse4Cer a2,3sia-lyltransferase Figure 1 Step 13), has been characterized in bovine spleen [147, 148], embryonic chicken brains [79, 130, 131], human colon carcinoma [79, 131, 132], melanoma WM266-4 cells [149], and human placenta [133]. 

The SAT that catalyzes the synthesis of sialyllactose was first detected in rat mammary tissue by Roseman and his co-workers (Jourdian et al., 1963 Carlson et al., 1973a). In fact, this was the first SAT to be characterized in an animal system, being detected later in embryonic chicken brain (Kaufman and Basu, 1966). However, the SAT activities that catalyze the transfer of sialic acid to lactose and to lactosylceramide appear to be different from the latter by all kinetic parameters (S. Basu, 1966 Kaufman and Basu, 1966 M. Basu et al., 1987 S. C. Basu, 1991). In addition to CMP-NeuAc lactose a2-3 sialyltransferase, CMP-NeuAc lactosamine a2-6 sialyltransferase (ST6N) was first characterized by Roseman and his co-workers (Bartholomew et al., 1973) from colostrum. The ST6N enzyme activity is ubiquitous and was purified by Hill and his associates... 

---