Genetic heterogeneity of membrane-bound beta-glucosidase in Gaucher's disease.

Membrane-bound beta-glucosidase of leukocytes exists in two forms, one with optimal activity at about pH 4.5, whereas the other is most active at pH 5.5-6.0. In one case of type 1 (adult) Gaucher's disease, the pH 4.5 activity was totally deficient, but the pH 5.5 activity was present in normal amounts; obligate heterozygotes had half the normal activity at pH 4.5. In two different cases, the membrane-bound beta-glucosidase was completely absent when assayed at either pH 4.5 or pH 5.5. Two further cases had residual activity at both ph values; however, the residual enzymes had different thermostability properties than the corresponding enzymes of control leukocytes. The results are consistent with the existence of at least three genetic variants of type 1 (adult) Gaucher's disease.