N-acetylgalactosamine-6-sulfatase

N-acetylgalactosamine-6-sulfatase (GALNS) is an enzyme that is encoded by the GALNS gene in humans. This enzyme is a member of the glycosaminoglycan metabolic pathway, and its deficiency is associated with a rare lysosomal storage disease known as Morquio A syndrome.

Function

N-acetylgalactosamine-6-sulfatase is a lysosomal enzyme that catalyzes the hydrolysis of the 6-sulfate groups of the N-acetyl-D-galactosamine 6-sulfate units of chondroitin sulfate and keratan sulfate. Deficiency of this enzyme results in the accumulation of undegraded substrate and leads to severe pathological conditions.

Clinical significance

Deficiency of N-acetylgalactosamine-6-sulfatase leads to Morquio A syndrome, a lysosomal storage disease. This disease is characterized by a deficiency in the catabolic pathway of the glycosaminoglycans, keratan sulfate and chondroitin-6-sulfate.

Symptoms of Morquio A syndrome include abnormal development of bones, a distinctive "bell-shaped" chest with a protruding sternum, short stature, and joint abnormalities. Other symptoms may include hearing loss, clouded corneas, heart disease, and spinal cord compression.

Genetics

The GALNS gene is located on the long (q) arm of chromosome 16 at position 24.3. The gene spans about 50 kb and contains 14 exons.

File:GALNS gene location.png

Location of the GALNS gene on chromosome 16

Treatment

There is currently no cure for Morquio A syndrome. Treatment is symptomatic and supportive, and may include physical therapy, surgical correction of bone abnormalities, and enzyme replacement therapy with recombinant human N-acetylgalactosamine-6-sulfatase.

See also

• Lysosomal storage disease
• Morquio syndrome
• Glycosaminoglycan
• Enzyme