The Effects of Acidic Lipids and Heat-Stable Factor on the Physical-Chemical and Kinetic Properties of Glucocerebrosidase
Part of the NATO ASI Series book series (NSSA, volume 116)
Glucocerebrosidase (glucocerebroside:ß-glucosidase, E.C.126.96.36.199) is a lysosomal enzyme whose deficiency is responsible for the sphingolipidosis, Gaucher’s disease1,2; it catalyzes the following reaction:
This membrane-bound enzyme can be solubilized by extraction of lysosomal membranes with detergents (e.g., sodium cholate, Triton X-100) and 1-butano13,4. However, such procedures disrupt the natural association of the enzyme with endogenous membrane lipids, thereby rendering glucocerebrosidase inactive. Reconstitution of ß-glucosidase activity can be achieved two ways. The first one requires incorporating a strong ionic detergent such as sodium taurocholate or taurodeoxycholate in the assay medium5’6. Unfortunately, while members of the bile salt family are generally effective activators of glucocerebrosidase, they present two problems: (1) they are not components of the lysosomal membrane, and as such are nonphysiologic, and (2) they obscure differences in the kinetic properties of the residual (5–20% of control) spleen glucocerebrosidase of patients with the nonneurologic form (type 1) and the more severe neurologic (types 2 and 3) forms of Gaucher’s disease4. The second way to reconstitute ß-glucosidase activity (determined using the water-soluble aryl glucoside substrate, 4-methylumbelliferyl-ß-D-glucopyranoside (MUG1c)) is to add acidic natural lipids, alone or in combination with a heat-stable activator protein (isolated from Gaucher spleen7), to the ß-glucosidase assay medium8–12. The present report describes the effects of acidic lipids and the heat-stable factor (HSF) on the physical-chemical and kinetic properties of glucocerebrosidase.
KeywordsCritical Micellar Concentration Sodium Taurocholate Sodium Cholate Acidic Lipid Partial Specific Volume
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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© Plenum Press, New York 1986