DEPENDENCE OF LYSOZYME ACTIVITY ON PH AND IONIC STRENGTH

1. 1. The activity of lysozyme (EC 3.2.1.17) towards cell suspensions of Micrococcus lysodeikticus has been examined as a function of ionic strength from pH 4-10. 2. 2. Initial increase in activity and subsequent inhibition of lytic activity with increase of ionic strength was much more marked at the higher pH values. 3. 3. The optimum pH for lysis varied markedly with the ionic strength and the maximum activity attained at pH 9.2 was greater than the maximum activity attained at pH 6.2 or below. These results are in contrast to the cleavage of the tetramer of N-acetyl-D-glucosamine (GlcNAc) from chitin. 4. 4. Inhibition of lysozyme by GlcNAc and (GlcNAc)2 was independent of ionic strength at pH 6.2 and 9.2, whilst inhibition by other N-acylglucosamines and anomers of methyl and ethyl N-acetylglucosaminides decreased markedly as the ionic strength was increased at both pH 6.2 and 9.2. Inhibition was always more effective in alkaline solution. 5. 5. The results are discussed in terms of the electrostatic interaction between positive charges on lysozyme and negative charges on the cell wall, that are absent from the oligosaccharides from chitin. © 1969.