Queratán sulfato: Diferenzas entre revisións
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As denominacións queratán sulfato tipo I (KSI) e queratán sulfato tipo II (KSII) foron asignadas orixinalmente baseándose no tipo de tecido do que procedía o queratán sulfato. O de tipo I foi illado da [[córnea]] e o de tipo II do [[esqueleto]].<ref>{{cite journal | author = Meyer K, Linker A. ''et al.'' | title = The mucopolysaccharides of bovine cornea | journal = J. Biol. Chem. | date=1 December 1953| volume=205 | issue=2 | pages=611–616 | url= http://www.jbc.org/cgi/reprint/205/2/611 | pmid = 13129238 }}</ref><ref>{{cite journal | author = Meyer K, Hoffman P. and Linker A. | title = Mucopolysaccharides of Costal Cartilage | journal = Science | year=1958 | volume=128 | issue=3329 | pages=896 | url= http://www.sciencemag.org/cgi/reprint/128/3329/896| pmid = 13592269 | doi = 10.1126/science.128.3329.896}}</ref> Existen algunhas diferencias menores na composición [[monosacárido|monosacarídica]] entre os queratán sulfatos extraídos de ambos os tecidos e incluso entre os extraídos dun mesmo tecido. Porén, as principais diferenzas están no modo en que cada tipo de queratán sulfato se une ás proteínas.<ref>{{cite journal | author = Seno N, Meyer K. ''et al.'' | title = Variations in Keratosulfates | journal = J. Biol. Chem. | date=1 March 1965| volume=240 | pages=1005–1019 | url= http://www.jbc.org/cgi/reprint/240/3/1005 | pmid = 14284693 | issue = 3 }}</ref> De feito, as denominacións KSI e KSII están hoxe baseadas nestas diferencias na unión ás proteínas. Os queratán sulfatos de tipo I tis [[Glycans#N-Linked glycans|N-linked]] to specific [[asparagine]] [[amino acid]]s via [[N-Acetylglucosamine|''N''-acetylglucosamine]] and KSII is [[Glycans#O-Linked glycans|O-linked]] to specific [[Serine]] or [[Threonine]] amino acids via [[N-acetyl galactosamine]].<ref>{{cite journal | author = Nieduszynski IA, Huckerby TN. ''et al.'' | title = There are two major types of skeletal keratan sulphates | journal = Biochem. J. | year=1990 | volume=271 | issue=1 | pages=243–245 | pmid = 2222415 | pmc = 1149539}}</ref> The tissue based classification of KS no longer exists as KS types have been shown to be non tissue specific.<ref name=funderburgh/> A third type of KS (KSIII) has also been isolated from [[brain]] tissue that is O-linked to specific serine or threonine amino acids via [[mannose]].<ref>{{cite journal | author = Krusius T, Finne J. ''et al.'' | title = Identification of an O-glycosidic mannose-linked sialylated tetrasaccharide and keratan sulfate oligosaccharides in the chondroitin sulfate proteoglycan of brain | journal = J. Biol. Chem. | date=25 June 1986| volume=261 | issue=18 | pages=8237–8242 | url= http://www.jbc.org/cgi/reprint/261/18/8237 | pmid = 2941416 }}</ref>
A cantidade de queratán sulfato atopado na córnea tipo I é 10 veces maior ca na cartilaxe e de 2 a 4 veces maior ca noutros tecidos.<ref>{{cite journal | author = Funderburgh JL, Caterson B. and Conrad GW. | title = Distribution of proteoglycans antigenically related to corneal keratan sulfate proteoglycan | journal = J. Biol. Chem. | year=1987 | volume=262 | issue =24 | pages=11634–11640 | pmid = 2957372}}</ref> Prodúceno os [[queratocito]]s corneais <ref name="pmid12933807">{{cite journal |author=Funderburgh JL, Mann MM, Funderburgh ML |title=Keratocyte phenotype mediates proteoglycan structure: a role for fibroblasts in corneal fibrosis |journal=[[J. Biol. Chem.]] |volume=278 |issue=46 |pages=45629–37 |year=2003 |month=November |pmid=12933807 |doi=10.1074/jbc.M303292200 |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=12933807 |pmc=2877919}}</ref> e pénsase que desempeña o papel de tampón dinámico para a hidratación da córnea. Nun trastorno progresivo raro chamado [[distrofia corneal macular]], a síntese de queratán sulfato está ausente ou é anormal <ref name="OMIM_MCDC">[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=217800 Macular dystrophy, corneal, 1] - OMIM</ref>.
No queratán sulfato de tipo I non corneal, as cadeas de queratán sulfato únense por enlace por N (''N-linked'') ás proteínas [[osteoadherina]], [[
===KSII===
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