Galactosyltransferase inhibition

Prieels et al. (1976) studied the binding of glycoconjugates with galactosyltransferase in both the presence and absence of a-lactalbumin. They concluded that, in contrast to its ability to inhibit AT-acetyllactos-amine production, a-lactalbumin does not inhibit the transfer of d-galactose to oligomers of A -acetylglucosamine or to glycopeptides. 

The j8-galactosidase from the Pencillium simplicissimum isolated from soil has high galactosyltransferase activity Synthesis of galactoohgosaccharides from 3 to 4 units of monosaccharide. When monosaccharides are present in the reaction system, the transfer activity of the enzyme will be inhibited, so only by the enzyme from P. simplicissimum cultured under the non-optimum hydrolysis conditions, galactooligosaccharide production can reach the maximum. For example, the lactose solution (concentration of 60%) incubated at pH 6.5 and 50 C obtained the maximum conversion rate. The product composition was 30.5% galacto-ohgosaccharide, 27.5% residual lactose and 42% free monosaccharides. 

A D-galactosyltransferase (pH optimum 6) requiring Mg + or Mn + ions has been found in alveolar lung cells UDP is a non-competitive inhibitor of the enzyme. High concentrations of cycloheximide competitively inhibited a D-galactosyltransferase present in isolated Golgi membranes from rat liver the effect of the inhibitor appears to be primarily on the membrane, affecting the enzyme secondarily. The observation that Zn +, Cd +, Fe " , Co +, and... 

Membrane-bound 2-acetamido-2-deoxy-a- and -)8-D-galactosyltransferases from guinea-pig microsomes were able to catalyse the formation of the nonreducing, terminal residues of Forssman hapten and globoside, respectively. The enzymes can be readily differentiated, since the a-transferase is inhibited, and the -transferase is stimulated, by UDP UDP-D-glucose can suppress both a-transferase and pyrophosphatase activities. 

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