Activity and distribution of bacteriolytic N-acetyl-muramidase during growth of Acanthamoeba castellanii in axenic culture

Abstract

Bacteriolytic endo N-acetylmuramidase of Acanthamoeba castellanii has been studied. In amoeba cells the enzyme, like exo N-acetylglucosaminidase and acid phosphatase, is attached to the lysosomes, as it is sedimentable when homogenates are prepared in medium containing sucrose. The sedimentability could be abolished by treatment with Triton X-100, thermal disintegration or by osmotic shock. The sedimentability and acid pH optima of the enzyme are highly characteristic of lysosomes. However, in young cultures over 50 per cent of enzyme activity was secreted by amoeba cells to the environment. The enzyme activity changed with the phase of growth cycle. The activity of enzyme expressed as units per mg of amoeba protein or per constant number of cells has been found to increase over 10 fold on aging of amoeba cultures. The increase in enzyme activity was stopped by actidione. The possible mechanisms of the regulation of the activity of lysosomal enzyme synthesis by amoebae are discussed.