MODIFICATION OF LYSINE AND ARGININE RESIDUES OF LYSOZYME AND EFFECT ON ENZYMATIC ACTIVITY

1. 1. Acetylation of all six lysine residues of lysozyme (EC 3.2.1.17) abolished lytic action towards cell of Micrococcus lysodeikticus in 0.05 M phosphate buffer (pH 6.2) but did not affect cleavage of the treatment of N-acetylglucosamine (GlcNAc)4 obtained from chitin. 2. 2. Acetylated lysozyme stil lysed cells in solution of low ionic strength at pH 6.2. Compred with unmodified enzyme the activity profile for acetyl lysozyme was displaced to much lower values of ionics strength and was still markedly dependent on pH. 3. 3. Chemical modification of the lysine groups with ehtyl acetamidate increased the activity towards cells slightly, yet did not alter the activity towards (GlcNAc)4. 4. 4. Modification of seven out of eleven arginine residues with 2,3-butanedione in borate buffer reduced the activity of acetyl lysozyme towards cells but not towards (GlcNAc)4. 5. 5. Since all the basic residues of lysozyme apparently lie outside the active centre, the persistence of lytic activity over a very wide pH range is discussed in terms of the currently accepted mechanism of action of lysozyme. © 1969.