Some studies on catalysis by lysozyme

The preparation of some aryl β-glycosides of β-1, 4-linked oligosaccharides of (GlcNAc)_n, n = 2, 3, 4, is described. These compounds were tested as substrates for lysozyme from hens' egg white. The best of them, (GlcNAc)₄-3,4-DNP, had a value of k_cat/K_m which was about one-nintieth that for the hydrolysis of (GlcNAc)₆. The pH dependence of k_cat and k_cat/K_m for the hydrolysis of (GlcNAc)₄-3,4-DNP was similar to that for (GlcNAc)₆. (GlcNAc)₄-3,4-DNP was also a substrate for human lysozyme and lysozyme from ducks' egg white (II and III). An impure sample of (GlcNAc)₂F was prepared and this was hydrolyzed much more rapidly than (GlcNAc)₂-2,4-DNP by lysozyme. Compounds of type (GlcNAc)_n−1(XylNAc)Ar, where n = 2, 3, 4, were prepared and found not to be substrates for lysozyme. In the presence of (GlcNAc)₄ or (GlcNAc)₅, lysozyme-induced hydrolyses of (GlcNAc)-3,4-DNP and (Glc)-3,4-DNP were observed but not of (XylNAc)-3,4-DNP, (6-deoxy-GlcNAc)-3,4-DNP, (6-F-GlcNAc)-3,4-DNP, and (6-Cl-GlcNAc)-3,4-DNP. The significance of these results is discussed.