Diferenzas entre revisións de «Queratán sulfato»

 
* Rexión de unión. Situada no extremo por onde a cadea de queratán sulfato se une ás proteínas para formar o proteoglicano.
* A rexión repetitiva. Está composta por unidades repetidas do disacárido -3[[galactosa]]β1-4[[N-acetilglicosamina]]β1-.
* A rexión tope ou carapuchaterminal. Está situada na cadea no extremo oposto da rexión de unión á proteína.
 
O monosacárido [[manosa]] aparece na rexión de unión no queratán sulfato tipo I. Nos queratán sulfatos tipo II os disacáridos da rexión repetitiva poden estar [[fucosa|fucosilados]]. En todos os queratán sulfatos tipo II e no 70 % dos de tipo I atopamos [[ácido N-acetilneuramínico]] no extremo da rexión terminal <ref name=funderburgh>{{cite journal | author = Funderburgh JL. | title = Keratan sulfate: structure, biosynthesis, and function | journal = Glycobiology | year=2000 | volume=10 | issue =10 | pages=951–958 | pmid = 11030741 | doi = 10.1093/glycob/10.10.951}}</ref>.
 
===Tipos de queratán sulfato===
TheAs designationsdenominacións queratán sulfato tipo I (KSI) ande KSIIqueratán weresulfato originallytipo assignedII on(KSII) theforon basisasignadas oforixinalmente thebaseándose tissueno typetipo fromde whichtecido thedo keratanque sulfateprocedía waso isolatedqueratán sulfato. KSIO wasde isolatedtipo fromI foi illado da [[cornealcórnea]] tissuee ando KSIIde fromtipo II do [[skeletalesqueleto]] tissue.<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> MinorExisten monosaccharidealgunhas compositionaldiferencias differencesmenores existna betweencomposición KS[[monosacárido|monosacarídica]] extractedentre fromos bothqueratán sourcessulfatos andextraídos evende KSambos extractedos fromtecidos thee sameincluso sourceentre os extraídos dun mesmo tecido. HoweverPorén, majoras differencesprincipais occurdiferenzas inestán no modo theen wayque eachcada KStipo typede isqueratán joinedsulfato tose itsune coreás proteinproteínas.<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> TheDe designationsfeito, as denominacións KSI ande KSII areestán nowhoxe basedbaseadas uponnestas thesediferencias proteinna linkageunión differencesás proteínas. KSIOs queratán sulfatos de tipo I istis [[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>
 
===Corneal KSI===
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