Specificity of bacteriolytic enzyme II from a soil amoeba, Hartmannella glebae

Two bacteriolytic enzymes were produced when Hartmanella glebae was grown in the presence of both Enterobacter aerogenes and Alcaligenes faecalis. The identification of enzyme I as N-acetylmuramidase was reported earlier. Enzyme II was purified by gel filtration on a Bio-Gel A column. A recovery of 68.76% with 72.3-fold purification was obtained. It was found that 5 and 10 mM MgCl2 significantly increased the bacteriolytic activity. It is a basic protein. The cell walls of Micrococcus lysodeikticus were lysed by the enzyme, and the products of digestion were purified by Amberlite CG-120 and Sephadex G-15 chromatography to facilitate the detection of amino sugars. After reduction of the oligosaccharides with sodium borohydride and acid hydrolysis, the amino sugars were identified by paper chromatography. It was found that enzyme II cleaved the glycosidic bond between N-acetylmuramic and and N-acetylglucosamine of the peptidoglycan moiety of the cell walls. Thus, the enzyme was identified as endo-beta-N-acetylmuramidase.