Enzymatic syntheses of T antigen-containing glycolipid mimicry using the transglycosylation activity of endo-α-N-acetylgalactosaminidase

Thomsen-Friedenreich antigen (T antigen) disaccharide, beta -D-galactose-(1 --> 3)-alpha -N-acetyl-D-galactosamine (beta -D-Gal-(1 --> 3)-alpha -D-GalNAc), containing glycolipid mimicry was synthesized using the transglycosylation activity of endo-alpha -N-acetylgalactosaminidase from Bacillus sp. This enzyme could transfer the disaccharide from a p- nitrophenyl substrate to water-soluble 1-alkanols and other alcohols at a transfer ratio of 70% or more. Although the transfer ratios were lower for water-insoluble than water-soluble alcohols, they were shown to increase by adding sodium cholate to the reaction mixtures. The enzyme also transferred the disaccharide directly from asialofetuin to l-alkanols. The anomeric bond between the disaccharide and l-alkanols of the transglycosylation product is in the alpha configuration as determined by sequential digestion of jack bean beta -galactosidase and Acremonium alpha -N- acetylgalactosaminidase. Since the transglycosylation product, beta -D-Gal-(1--> 3)-alpha -D-GalNAc-(1 -->O)-hexyl, efficiently inhibits the binding of anti-T antigen monoclonal antibody to asialofetuin, it has potential as an agent for blocking T antigen-mediated cancer metastasis. (C) 2001 Elsevier Science Ltd. All rights reserved.