Galactosyl transferases transferase

A large number (>50) of glycosyltransferases and other types of transferase are required to synthesize pectic polysaccharides [20]. The activities of several glycosyltransferases have been identified in cell-free membrane preparations from plants. However, only a few of these enzymes have been partially characterized and shown to be involved in pectin biosynthesis. These include D-galacturonosyl transferase, galactosyl transferase, arabinosyl transferase, and apiosyl transferase [20]. An enzyme that catalyzes the methylesterification of homogalacturonan (homogalatur-onan methyltransferase) has been partially characterized [20]. There are also reports that plants contain methyltransferases that catalyze the methylesterification of RG-I and RG-II [25]. No 0-acetyl transferase involved in pectin biosynthesis has been characterized nor have the enzymes that catalyze the addition of phenolic acids to pectins [20]. 

Deppert, W., Werchau, H., and Walter, G., 1974, Differentiation between intracellular and cell surface glycosyl transferases. Galactosyl transferase activity in intact cells and in cell homogenate, Proc. Natl. Acad. Sci. U.S. 71 3065. 

FIGURE 6.20 A disaccharide of galactose and glucose is covalently linked to the 5-hydroxyl group of hydroxylysines in collagen by the combined action of the enzymes galactosyl transferase and glucosyl transferase. 

Another interesting point is that glucosyl transferase and galactosyl transferase apparently exerted different activities depending on the blueberry cultivar. ... 

Mutant or knockout mice defective in specific enzymes involved in lipid synthesis have provided powerful tools for genetic analysis of lipid function in the nervous system. For example, disruption of the genes for ceramide galactosyl transferase or galactosyl ceramide sulfotransferase,... 

Monosaccharide attachment to some of the hydroxylysine residues within the a chains occurs at this stage as galactose (gal) and glucose (glc) residues are added by specific galactosyl transferase and glucosyl transferases. The carbohydrates are attached as single monosaccharides or as gal-glc disaccharides. 

Scheme 10.1 Glycopeptide synthesis and a-chymotrypsin catalyzed release from the solid support, a) 25% TFA (CH2CI2) b) 0-(N-Boc-Phe)glycolic acid (7 eq), BOP, HOBt, DIEA b) 25% TFA (CH2CI2) c) Boc-Gly-OH (7 eq), BOP, HOBt, DIEA c) 25% TFA (CH2CI2) d) Boc-Asn(GlcNAcb)-OH (3 eq), BOP, DIEA e) galactosyl transferase, sialyl transferase f) CT, H2O, pH 7.0 g) ultrafiltration h) a-l,3-fuco-syltransferase, GDP-Fuc (2.5 eq), 0.1 M HEPES (pH 7.0), 95%.

Scheme 10.2 Oligosaccharide synthesis and a-chymotrypsin catalyzed release from the solid support, a) Z-Phe-NH-(CH2)6-OH (7), CSA, (CHCljjz, 70°C b) Hj, Pd/C, MeOH, 50°C c) CH2 = CHCONH(CHjjsCOOH (8), EtOH-CeHe d) MeONa (cat.), MeOH/THF, CH2 = CHCONH2, TMEDA, APS, DMSO-H2O, SOT e) Galactosyl transferase, Sialyl transferase g) CT, Tris-HCI buffer, pH 7.8, 48 °C, 72% from (10).

LIPOPOLYSACCHARIDE N-ACETYLGLU-COSAMINYLTRANSFERASE LIPOPOLYSACCHARIDE GALACTOSYL-TRANSFERASE... 

Powell, J. T. and Brew, K. 1975. On the interaction of a-lactalbumin and galactosyl-transferase during lactose synthesis. J. BioL Chem. 250, 6337-6343. 

The enzymes involved are nucleoside diphosphohexosetransferases, probably GDP-D-mannosyltransferase (EC 2.4.1.32) and UDP-D-galactosyl-transferase. For a structurally related polymer, (1 - 6)-a-D-xylosyl-(l - 4)-/3-D-glucan, synthesis was shown to involve concurrent incorporation of D-xylose and D-glucose, and not substitution by D-xylose of a preformed (1 - 4)-/3-D-glucan chain.34 The insolubility of (1 - 4)-/3-D-glucan and man-nan would make the latter mechanism unlikely. 

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