[Enrichment and characterization of a bacteriolytic amoebic enzyme].

Extracts of cultures of a small free-living amoeba, which feeds mainly on gram-negative bacteria, are capable of lysing heat-killed gram-negative bacteria. The lytic activity was enriched 36-fold by means of precipitation with (NH4)2S04 and of chromatography on Sephadex G-75, followed by ultrafiltration. The activity is less resistant to heat than is lysozyme, and is optimal at 45 °C. The pH-optimum is at 6.5. The molecular weight corresponds to that of lysozyme from chicken eggwhite; the isoelecric point is at 10.0. The effect of the amoebic activity on cells of A. metalcaligenes and M. lysodeikticus is different from that of eggwhite lysozyme on the same cells. We conclude that the lytic activity of the amoeba is due to a lysozyme with a special mode of action.