| GBA (GBA1, glucocerebrosidase) is a lysosomal glycosidase in the sphingolipid catabolic pathway that hydrolyzes glucosylceramide to ceramide and glucose using a retaining mechanism with catalytic glutamate residues, which operate in the acidic lumen to form and resolve a covalent glycosyl–enzyme intermediate. The protein folds into a (β/α)₈‑like catalytic domain with auxiliary regions that support binding to the lysosomal membrane protein LIMP‑2 and formation of functional dimers, providing correct trafficking to lysosomes and a stable configuration for substrate recognition and catalysis. GBA activity decreases lysosomal glucosylceramide levels and generates ceramide that can be converted to more complex sphingolipids or further metabolized, and this enzymatic step contributes to the composition of lysosomal and cellular membranes as well as to pools of bioactive ceramide species. Changes in glucosylceramide and ceramide content influence the physical properties of lysosomal membranes and the efficiency of degradation of macromolecules delivered by endocytosis and autophagy, linking GBA activity to general lysosomal proteolysis and lipid recycling. Biallelic pathogenic variants in GBA cause Gaucher disease, which is characterized by deficient glucocerebrosidase activity, accumulation of glucosylceramide and related lipids in macrophage lysosomes, formation of lipid‑laden Gaucher cells, and enlargement and dysfunction of spleen, liver, and bone marrow. Heterozygous and homozygous GBA variants occur at higher frequency in Parkinson’s disease than in control populations, and reduced glucocerebrosidase activity is detected in brain tissue from carriers and non‑carriers with Parkinson’s disease. |
