A method is introduced for the assay of alkaline phosphatase in homogenates of cultured human skin fibroblasts. In a first group of 11 strains, a four- to fifteen-fold increase of enzyme activity is consistently observed following a period of starvation. In the remaining 31 cell-strains similar specific activities of alkaline phosphatase are found irrespective of medium changes. In regularly fed cultures, an inverse exponential correlation between the specific activity of alkaline phosphatase and the age of the donor has been detected.
Isozymes of N-acetyl-beta-D-hexosaminidase in body fluids, culture medium, postmortem organs, and cultured fibroblasts from patients with I-cell disease were resolved by ion exchange column chromatography. The elution pattern was compared in detail with that of the isozymes in control samples. This approach revealed no qualitative differences between the isozymes from the two sources. There is a relative increase of the neuraminidase-sensitive components of hexosaminidase in I-cell disease. This phenomenon is probably related less to the unknown primary defect of the disorder than to the quantitative change in the distribution of hexosaminidase components between the intra- and the extracellular compartment.
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