title: Human xylosyltransferase II is involved in the biosynthesis of the uniform tetrasaccharide linkage region in chondroitin sulfate and heparan sulfate proteoglycans.
abstract: Human xylosyltransferase I (XT-I) initiates the biosynthesis of the glycosaminoglycan (GAG) linkage tetrasaccharide in proteoglycans. Xylosyltransferase II (XT-II) is a protein homologous to XT-I but with hitherto unknown activity or physiological function. Here, we report the enzymatic activity of XT-II and provide evidence that XT-II initiates the biosynthesis of both heparan sulfate and chondroitin sulfate GAGs. Transfection of the xylosyltransferase-deficient Chinese hamster ovary mutant pgsA-745 with XT-I or XT-II coding cDNA completely restored GAG biosynthesis. GAG disaccharide analysis revealed that XT-I- and XT-II-transfected pgsA-745 cells produced similar amounts of chondroitin sulfate and heparan sulfate. Furthermore, a high xylosyltransferase activity was measured after transfection with cDNAs encoding either isozyme. Analysis of the enzyme activity revealed that XT-II catalyzes the transfer of xylose to similar peptide acceptors as XT-I but with different efficiency. The optimal XT-II acceptor was observed using a bikunin-related peptide (K(m) 5.2 microM). Analysis of XT-I and XT-II mRNA expression in murine tissues showed a differential expression pattern for both enzymes. In particular, XT-II is highly expressed in liver tissue, where XT-I transcripts were not detected. This is the first report on the enzyme activity of XT-II and its involvement in chondroitin sulfate and heparan sulfate biosynthesis.
authors.affiliation: Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, 32545 Bad Oeynhausen, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Pönighaus
authors.forename: Michael
authors.initials: M
authors.lastname: Ambrosius
authors.forename: Javier Carrera
authors.initials: JC
authors.lastname: Casanova
authors.forename: Christian
authors.initials: C
authors.lastname: Prante
authors.forename: Joachim
authors.initials: J
authors.lastname: Kuhn
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Esko
authors.forename: Knut
authors.initials: K
authors.lastname: Kleesiek
authors.forename: Christian
authors.initials: C
authors.lastname: Götting
mesh_terms: D000818:Animals; D016466:CHO Cells; D002236:Carbohydrate Conformation; D002809:Chondroitin Sulfates / Q000096:biosynthesis* / Q000235:genetics; D006224:Cricetinae; D003412:Cricetulus; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006497:Heparan Sulfate / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D009844:Oligosaccharides / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity / Q000502:physiology; D010430:Pentosyltransferases / Q000096:biosynthesis* / Q000235:genetics; D000097608:UDP Xylose-Protein Xylosyltransferase
chemical_list: D002809:Chondroitin Sulfates; D006497:Heparan Sulfate; D007527:Isoenzymes; D009844:Oligosaccharides; D010430:Pentosyltransferases; D000097608:UDP Xylose-Protein Xylosyltransferase