N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase (phosphodiester alpha-GlcNAcase, mannose 6-phosphate-uncovering enzyme, NAGPA)

Function

• protein glycosylation
• catalyzes 2nd step in formation of mannose 6-phosphate targeting signal on lysosomal enzyme oligosaccharides by removing GlcNAc residues from GlcNAc-alpha-P-mannose moieties, which are formed in the 1st step

glycoprotein N-acetyl-D-glucosaminyl-phospho-D-mannose + H2O
                   <-->
N-acetyl-D-glucosamine + glycoprotein phospho-D-mannose

Structure

• homotetramer arranged as two disulfide-linked homodimers
• Tyr-based internalization signal may be essential for its retrieval from the plasma membrane to the trans-Golgi
• C-terminal NPFKD sequence may be endocytosis signal acting at plasma membrane or trans-Golgi to return the enzyme to the cis/medial-Golgi
• contains 1 EGF-like domain

Compartment

cis/medial Golgi

Alternative splicing

named isoforms=3

Expression

may be brain specific

More general terms

• glycosidase (glycoside hydrolase)
• membrane protein
• glycoprotein

Database

• OMIM: https://mirror.omim.org/entry/607985
• UniProt: http://www.uniprot.org/uniprot/Q9UK23.html