Mannosidases capable of uncapping mannose-1-phospho-6-mannose linkages and demannosylating phosphorylated N-glycans and methods of facilitating mammalian cellular uptake of glycoproteins

1. A method of directing a glycoprotein to the interior of a mammalian cell, the glycoprotein comprising a mannose-1-phospho-6-mannose moiety, wherein the mannose residue that has a phosphate residue bound at the 6 position is linked to a terminal mannose residue at the 1 position of the terminal mannose residue, the method comprising contacting the cell with the glycoprotein after it has undergone:

(a) uncapping of the mannose-1-phospho-6-mannose moiety to mannose-6-phosphate on the glycoprotein; and

(b) removal of the terminal mannose residue,

wherein the glycoprotein that has undergone (a) and not (b) or (b) but not (a) does not substantially bind to a mannose-6-phosphate receptor on the cell,

wherein the glycoprotein that has undergone (a) and (b) does substantially bind to a mannose-6-phosphate receptor on the cell, and

wherein steps (a) and (b) are catalyzed by a single mannosidase enzyme that is a family 38 glycosyl hydrolase (GH38 family) mannosidase.

2. The method of claim 1 , wherein said glycoprotein is a human protein.

3. The method of claim 1 , wherein said glycoprotein is a pathogen protein, a lysosomal protein, a growth factor, a cytokine, a chemokine, an antibody or antigen-binding fragment thereof, or a fusion protein.

4. The method of claim 3 , wherein said lysosomal protein is a lysosomal enzyme.

5. The method of claim 4 , wherein said lysosomal enzyme is acid alpha glucosidase or alpha galactosidase.

6. The method of claim 1 , wherein said glycoprotein is associated with a lysosomal storage disease (LSD).

7. The method of claim 6 , wherein said LSD is Fabry's disease, mucopolysaccharidosis I, Farber disease, Gaucher disease, GM1-gangliosidosis, Tay-Sachs disease, Sandhoff disease, GM2 activator disease, Krabbe disease, metachromatic leukodystrophy, Niemann-Pick disease, Scheie disease, Hunter disease, Sanfilippo disease, Morquio disease, Maroteaux-Lamy disease, hyaluronidase deficiency, aspartylglucosaminuria, fucosidosis, mannosidosis, Schindler disease, sialidosis type 1, Pompe disease, Pycnodysostosis, ceroid lipofuscinosis, cholesterol ester storage disease, Wolman disease, Multiple sulfatase deficiency, galactosialidosis, mucolipidosis, cystinosis, sialic acid storage disorder, chylomicron retention disease with Marinesco-Sjögren syndrome, Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, Danon disease, or Geleophysic dysplasia.