The lysosomal enzyme α-L-fucosidase (FUCA1; EC 3.2.1.51; CAZy family GH29) removes fucose residues from fucosylated glycoconjugates, and its deficiency leads to the ultra-rare lysosomal storage disease (LSD) fucosidosis [Online Mendelian Inheritance in Man (OMIM) 230000], which is characterized by the progressive accumulation of fucosylated glycopeptides and glycolipids in urine and in lysosomes of many tissues (Michalski and Klein, 1999; Willems et al., 1991). Here, FUCA1 is linked to fucosidosis.