Assay of the β‐glucosidase activity with natural labelled and artificial substrates in cultivated skin fibroblasts from homozygotes and heterozygotes with the Norrbottnian type of Gaucher disease

Abstract
Fibroblasts from 13 homozygotes and 27 obligate heterozygotes with the Norrbottnian type of Gaucher disease and 17 controls were cultivated and assayed with five β‐glucosidase methods, two with D‐[glucose‐U‐14C] glucosylceramide and three with the artificial substrate 4‐methylumbelliferyl‐β‐glucoside. Two marker enzymes were assayed on the same cell samples, 4‐methylumbelliferyl‐β‐galactosidase and N‐acetyl‐β‐glucosaminidase. The β‐glucosidase activity of cultured fibroblasts, as measured with all five β‐glucosidase methods, was significantly lower (P < 0.001) for Gaucher homozygotes than heterozygotes. There was no overlap between fibroblasts from Gaucher homozygotes and the others with any of the β‐glucosidase methods used. The β‐glucosidase activity was also significantly lower (P< 0.001) for Gaucher heterozygotes than controls. However, none of the five β‐glucosidase assays differentiated between all Gaucher heterozygotes and controls, as several overlaps occurred in each assay.