GBA1 and Parkinson disease: The lysosomal enzyme levels of GBA as well as several other lysosomal enzymes (alpha-galactosidase, beta-hexosaminidase, beta-galactosidase and neuraminidase) (see Table 2) were reduced even further in PD patients, and the GSL substrate GlcCer progressively accumulated with age (Table 4) [60].