title: Determination of xylosyltransferase activity in serum with recombinant human bikunin as acceptor.
abstract: Xylosyltransferase (XT) is the chain-initiating enzyme of the biosynthesis of chondroitin sulfate. So far, XT activity has been detected by incorporation of [14C]xylose in chemically deglycosylated cartilage proteoglycan or silk fibroin. However, these acceptors allow no reliable determination in blood. We found that recombinant bikunin is an excellent acceptor for XT. The Michaelis-Menten constants for the xylosylation of silk, deglycosylated cartilage proteoglycans, and bikunin were 545, 155, and 0.9 micromol/L, respectively. With recombinant bikunin as acceptor, we developed a sensitive assay that allows a precise determination of XT activity in serum. We measured the serum XT activities of 500 blood donors and observed a considerable sex and age dependence. XT activities in men (0.77-1.50 mU/L) were approximately 30% higher than in women (0.58-1.20 mU/L) and reached a maximum in donors of approximately 40 years of age. During the menstrual cycle, serum XT activity showed a significant coincidence with the beta-estradiol concentration, and in the first trimester of pregnancy we observed a strong increase in serum XT activity.
authors.affiliation: Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Bad Oeynhausen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Weilke
authors.forename: T
authors.initials: T
authors.lastname: Brinkmann
authors.forename: K
authors.initials: K
authors.lastname: Kleesiek
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood; D000595:Amino Acid Sequence; D002809:Chondroitin Sulfates / Q000096:biosynthesis; D004958:Estradiol / Q000097:blood; D005260:Female; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D019476:Insect Proteins; D007700:Kinetics; D008297:Male; D008562:Membrane Glycoproteins; D008597:Menstrual Cycle / Q000097:blood; D008875:Middle Aged; D008969:Molecular Sequence Data; D010430:Pentosyltransferases / Q000097:blood*; D011247:Pregnancy; D011506:Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012680:Sensitivity and Specificity; D012727:Sex Characteristics; D047011:Silk; D014360:Trypsin Inhibitor, Kunitz Soybean; D014994:Xylose / Q000378:metabolism; D000097608:UDP Xylose-Protein Xylosyltransferase
chemical_list: D002809:Chondroitin Sulfates; D004958:Estradiol; D006023:Glycoproteins; D019476:Insect Proteins; D008562:Membrane Glycoproteins; D010430:Pentosyltransferases; D011506:Proteins; D011994:Recombinant Proteins; D047011:Silk; D014360:Trypsin Inhibitor, Kunitz Soybean; D014994:Xylose; D000097608:UDP Xylose-Protein Xylosyltransferase; C109148:SPINT2 protein, human