Reactome | Keratan sulfate/keratin metabolism

Keratan sulfate/keratin metabolism

Stable Identifier

R-HSA-1638074

Type

Pathway

Species

Homo sapiens

ReviewStatus

5/5

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Keratan sulfate (KS) (a glycosaminoglycan, GAG) is a linear polysaccharide that consists of the repeating disaccharide unit GlcNAc-Gal (N-acetylglucosamine-galactose). KS can perform a structural function and is found in bone, cartilage and the cornea. In joints, it also acts as a shock absorber due to its highly hydrated nature. There are several classes of KS, KSI, II and III. KSI is N-linked to asparagine (Asn) residues in the core protein and is predominantly found in the cornea. KSII is O-linked to serine (Ser) or Thr (threonine) residues in the core protein and is found predominantly in cartilage linked to the protein aggrecan, forming the most abundant proteoglycan in cartilage. A third class of KS, KSIII, are proteoglycans in the brain. KSIII chains are linked to Ser/Thr residues in the core protein via mannose (Funderburgh 2000, Funderburgh 2002).

Normally, the body degrades GAGs as a natural turnover. Defects in the degradative enzymes cause the autosomal recessive mucopolysaccharide storage disease Morquio's syndrome (also called mucopolysaccharidosis IV). This involves the build up of KS in lysosomes, manifesting clinically as skeletal, dental and corneal abnormalities (Tomatsu et al. 2005).

Literature References

PubMed ID	Title	Journal	Year
11030741	Keratan sulfate: structure, biosynthesis, and function Funderburgh, JL	Glycobiology	2000
12512857	Keratan sulfate biosynthesis Funderburgh, JL	IUBMB Life	2002
16287098	Mutation and polymorphism spectrum of the GALNS gene in mucopolysaccharidosis IVA (Morquio A) Orii, T, Montaño, AM, Tranda Firescu, GG, Tomatsu, S, Nishioka, T, Lopez, P, Peña, OM, Gutierrez, MA, Noguchi, A, Yamaguchi, S	Hum Mutat	2005