N-acetylglucosaminidase, alpha is a protein that in humans is encoded by the NAGLU gene.
This gene encodes an enzyme that degrades heparan sulfate by hydrolysis of terminal N-acetyl-<small>D</small>-glucosamine residues in N-acetyl-alpha-D-glucosaminides.
Defects in this gene are the cause of mucopolysaccharidosis type IIIB (MPS-IIIB), also known as Sanfilippo syndrome B. This disease is characterized by the lysosomal accumulation and urinary excretion of heparan sulfate.