Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The Acceptor Binding Area of (1→4)-β-D-Galactosyltransferase Can Be Covalently Modified by Photoaffinity Labelling in the Presence of Photolabile LigandsThree spacer-modified oligosaccharides (SMOs) 2, 3, and 4, consisting of two nonreducing GlcNAc end groups, O-linked by an acyclic 10-membered spacer carrying azi groups in positions 2, 3, or 5, proved to be acceptor substrates for (1→4)-β-D-Galactosyltransferase (Gal-T) and models of the natural biantennary core heptasaccharide of N-glycoproteins. Photoaffinity labelling with each compound takes place with different efficiencies. This is an indication of regioselective chemical modification of the enzyme's extended binding area, because the reactive carbene in each case is placed in a different chemical surrounding. A radioactive SMO was used to prove the irreversible chemical modification of the acceptor binding site.
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