Xylosyltransferase II is the predominant isoenzyme which is responsible for the steady-state level of xylosyltransferase activity in human serum.
In mammals, two active xylosyltransferase isoenzymes (EC 2.4.2.16) exist. Both xylosyltransferases I and II (XT-I and XT-II) catalyze the transfer of xylose from UDP-xylose to select serine residues in the proteoglycan core protein. Altered XT activity in human serum was found to correlate directly with various diseases such as osteoarthritis, systemic sclerosis, liver fibrosis, and pseudoxanthoma elasticum. To interpret the significance of the enzyme activity alteration observed in disease states it is important to know which isoenzyme is responsible for the XT activity in serum. Until now it was impossible for a specific measurement of XT-I or XT-II activity, respectively, because of the absence of a suitable enzyme substrate. This issue has now been solved and the following experimental study demonstrates for the first time, via the enzyme activity that XT-II is the predominant isoenzyme responsible for XT activity in human serum. The proof was performed using natural UDP-xylose as the xylose donor, as well as the artificial compound UDP-4-azido-4-deoxyxylose, which is a selective xylose donor for XT-I.
Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Georgstraße 11, 32545 Bad Oeynhausen, Germany. Electronic address: jkuhn@hdz-nrw.de.
Joachim
J
Kuhn
MVZ Labor Limbach Nürnberg, Lina-Ammon-Strasse 28, 90471 Nürnberg, Germany.
Christian
C
Götting
Department of Chemistry and Molecular and Cell Biology Howard Hughes Medical Institute University of California, Berkeley, CA 94720, USA.
Brendan J
BJ
Beahm
Department of Chemistry and Molecular and Cell Biology Howard Hughes Medical Institute University of California, Berkeley, CA 94720, USA.
Carolyn R
CR
Bertozzi
Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Georgstraße 11, 32545 Bad Oeynhausen, Germany.
Isabel
I
Faust
Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Georgstraße 11, 32545 Bad Oeynhausen, Germany.
Patricia
P
Kuzaj
Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Georgstraße 11, 32545 Bad Oeynhausen, Germany.
Cornelius
C
Knabbe
Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Georgstraße 11, 32545 Bad Oeynhausen, Germany.
Doris
D
Hendig
D020134:Catalytic Domain; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007527:Isoenzymes / Q000097:blood / Q000378:metabolism; D008958:Models, Molecular; D010430:Pentosyltransferases / Q000097:blood* / Q000737:chemistry / Q000378:metabolism; D011509:Proteoglycans / Q000096:biosynthesis / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry; D014540:Uridine Diphosphate Xylose / Q000031:analogs & derivatives / Q000378:metabolism; D014994:Xylose / Q000378:metabolism; D000097608:UDP Xylose-Protein Xylosyltransferase
D007527:Isoenzymes; D010430:Pentosyltransferases; D011509:Proteoglycans; D011994:Recombinant Proteins; D012694:Serine; D014540:Uridine Diphosphate Xylose; D014994:Xylose; D000097608:UDP Xylose-Protein Xylosyltransferase
Glycosaminoglycan; Human serum; Mass spectrometry; Proteoglycan; Xylosyltransferase