1. An homogenate of liver biopsy taken from a patient with Pompe's disease (type II glycogen-storage disease) was analysed by enzyme microassay and subcellular fractionation by sucrose-density-gradient centrifugation.
2. A strikingly low activity of lysosomal acid α-d-glucosidase was noted but there was also increased activity of neutral α-d-glucosidase (found in endoplasmic reticulum).
3. Activities of the acid hydrolases, acid phosphatase and β-N-acetyl-d-glucosaminidase, were elevated compared with those of controls. Measurement of latent β-N-acetyl-d-glucosaminidase activity and results of subcellular fractionation experiments, indicated a marked fragility of certain populations of lysosomes. Lysosomes containing predominantly acid phosphatase and β-d-glucuronidase activities appeared to have normal integrity.
4. Assessment of organelle pathology by enzyme microassay indicated low mitochondrial and peroxisomal enzyme activities. In addition there was evidence of mitochondrial damage as reflected by increased sucrose permeability and by ultrastructural studies.