UDP-galactosyl transferase

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. 

Treatment GM3 UDP GalNAc N-acetylgalactos-aminy1trans fe rase GM2 UDP Gal Galactosyl-transferase... 

Lactalbumin /galactosyl transferase Synthesis of lactose UDP-galaclose complex -t- glucose - lactose + UDP... 

Since the PSV may be a tubular network rather than a series of distinct vesicles, secretion of the components may not require extensive vesicle fusion with the plasma membrane. Secretion parallels loss of UDP-Gal polysaccharide galactosyl transferase that is localized in the Golgi [189,190] suggesting that multiple secretory pathways may be coordinated to form the spore coat. 

It has also been demonstrated that expensive substrates such as UDP-Gal can be readily prepared in situ by enzymatic conversion of the relatively inexpensive sugar nucleotide uridine 5 -diphospho-a-D-glucopyranose (UDP-Glc) using a UDP-Gal 4-epimerase enzyme. This system, coupled with an appropriate UDP-Gal transferase, provides more economic access to enzymatically galactosylated compounds. In these multienzyme systems, to increase enzyme efficiency and also avoid multiple fermentations for separate enzyme preparations, fusion proteins have been constructed that contain both the Gal-epimerase and Gal-transferase enzymes. The use of these fused enzyme systems has increased in the recent years as their catalysis of sequential reactions can have a kinetic advantage over the mixture of two separated enzymes since the product of the first enzyme travels a shorter distance before being captured by the next enzyme in the sequence. 

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