Occurrence of sialidase activity in two distinct and highly homogeneous populations of lysosomes prepared from the brain of developing mouse

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Abstract
Light and heavy lysosomes of mouse forebrain were separated from each other by centrifugation on a Percoll gradient. Light lysosomes were then freed from mitochondria and membranes by sucrose density gradient centrifugation and further purified by floatation‐centrifugation on a sucrose gradient. The final preparations of light and heavy lysosomes, fairly homogenous, carried sinlidase activity, assayed on MU‐NeuAc. The optimal pH was 4.0 and 4.2, the apparent Km value 2.8 × 10−3 M and 4.2 × 10−3 M and the apparent V max value 0.11 and 0.47 mU mg−1 protein, for the light and heavy lysosome sialidase, respectively. From 4 days to adulthood the specific activity of the light and heavy lysosome sialidase increased 3‐fold and 1.7‐fold, respectively.