Commercial HLZ and purified rHLZ were incubated in sodium acetate buffers of pH 2–5, potassium dihydrogen phosphate buffers of pH 6–8, and carbonate bicarbonate buffers of pH 9–11 for 20 min. The lysozyme activity was then assayed, using the turbidimetric method, against Micrococcus lysodeikticus in potassium dihydrogen phosphate buffer, pH 7, at salt concentration of 0.05 M. The lytic activity incubated in potassium dihydrogen phosphate buffer, pH 7, at salt concentration of 0.05 M represented 100% activity. HLZ represents commercial HLZ; rHLZ represents purified rHLZ. The experiment for each group was repeated at least three times, and the results represent mean ± S.D.