The Biochemical Basis of MPS VI

MPS VI is one of a group of 7 types of inherited genetic diseases collectively called mucopolysaccharidoses, or MPS disorders.

Each type of MPS is caused by one of 11 inherited enzyme deficiencies, rendering the affected individuals unable to degrade specific glycosaminoglycans (GAGs). In the case of MPS VI, there is a deficiency of the enzyme N-acetylgalactosamine 4-sulfatase (also called arylsulfatase B, or ASB), which catalyzes one step in the breakdown of the GAG dermatan sulfate (DS). GAGs are a major component of connective tissue, and so are present throughout the body, particularly in the connective tissue of the skin, heart valves, airways, and skeleton. Lack of arylsulfatase B causes excess DS to accumulate in the cells of these and other tissues, causing widespread clinical manifestations that most often emerge in early childhood but can also appear later in life.¹

	Biochemical Basis of MPS VI. This disorder arises from an inherited deficiency of the enzyme N-acetylgalactosamine 4-sulfatase (also called arylsulfatase B), which catalyzes one step in the degradation of a glycosaminoglycan (GAG) called dermatan sulfate (DS). Adapted from Neufeld EF, Muenzer J. The mucopolysaccharidoses. In: Scriver CR, et al, eds. The Metabolic and Molecular Bases of Inherited Disease. Vol 3. 8th ed. New York: McGraw-Hill; 2001:3421–3452.
	A Lysosomal Storage Disorder. MPS VI is a lysosomal storage disorder. Excess GAG accumulate in lysosomes, where they would normally be degraded. The photo on the right shows lysosomes engorged with GAG.

1. Neufeld EF, Muenzer J. The mucopolysaccharidoses. In: Scriver CR, Beaudet AL, Sly WS, Valle D, eds. The Metabolic and Molecular Bases of Inherited Disease. Vol 3. 8th ed. New York, NY: McGraw- Hill; 2001:3421-3452.