PathwayStep1046 PathwayStep1047 PathwayStep1048 PathwayStep1045 PathwayStep1044 PathwayStep1043 Keratan sulfate degradation Authored: Jassal, B, 2011-12-01 Edited: Jassal, B, 2011-12-01 GENE ONTOLOGYGO:0042340 Keratan sulfate proteoglycans (KSPGs) are degraded in lysosomes as part of normal homeostasis of glycoproteins. Glycoproteins must be completely degraded to avoid undigested fragments building up and causing a variety of lysosomal storage diseases. KSPGs are Asn-linked glycoproteins and are acted upon by exo-glycosidases to release sugar monomers. The main steps of degradation are shown representing the types of cleavage reactions that occur so the full degradation of KS is not shown to avoid repetition. The proteolysis of the core protein of the glycoprotein is not shown here (Winchester 2005, Aronson & Kuranda 1989). Pubmed15647514 Pubmed2531691 Reactome Database ID Release 432022857 Reactome, http://www.reactome.org ReactomeREACT_121313 Reviewed: D'Eustachio, P, 2012-03-28 Beta-hexosaminidase A (BHEXA) cleaves the terminal GalNAc from keratan sulfate Beta-galactosidase (GLB1) can cleave galactose from a glycosaminoglycan N-acetylglucosamine 6-sulfatase (GNS) hydrolyses 6-sulfate groups of the N-acetyl-D-glucosamine 6-sulfate units of keratan sulfate Keratan sulfate is cleaved from its proteoglycan by an unknown galactosidase N-acetylgalactosamine-6-sulfatase (GALNS) hydrolyses the sulfate groups of galactose 6-sulfate units of keratan sulfate Extracellular KSPG translocates to the lysosome for degradation