Xylosylation of alternatively spliced isoforms of Alzheimer APP by xylosyltransferase.
Acceptor affinities of UDP-D-xylose:proteoglycan core protein beta-D-xylosyltransferase (XT) recognition signals in synthetic L-APP and L-APLP2 homologous peptides were determined. The Michaelis-Menten constants (KM) of the L-APP peptide TENEGSGLTNIK and the L-APLP2 peptide SENEGSGMAEQK were 20.1 and 18.9 microM, respectively. Therefore, the peptides proved to be as good acceptors for XT as the bikunin aminoterminus homologous peptide (KM = 22 microM). Due to the occurrence of L-APP and L-APLP2 transcripts in human brain tissue, XT activity was measured in human liquor cerebrospinalis. Mean values were calculated as 0.22 mU/L in males and 0.47 mU/L in females without disturbance of blood brain barrier. In addition, in homogenized rat brain tissue a mean XT activity of 0.75 mU/L was determined. Furthermore, XT activity was investigated in 21 different human cell lines. In 7 cell lines an enzyme activity was not detected in either extracellular space or cytoplasma. Our findings indicate that XT is not ubiquitously expressed in human cell types.
Götting
C
C
Institut für Laboratoriums- und Transfusionsmedizin, Herz-und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Bad Oeynhausen, Germany.
Kuhn
J
J
Brinkmann
T
T
Kleesiek
K
K
D017398:Alternative Splicing; D000544:Alzheimer Disease; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002460:Cell Line; D005260:Female; D006801:Humans; D008297:Male; D010430:Pentosyltransferases / Q000097:blood / Q000378:metabolism*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry*; D051381:Rats; D011917:Rats, Inbred Lew; D000097608:UDP Xylose-Protein Xylosyltransferase
D016564:Amyloid beta-Protein Precursor; D010430:Pentosyltransferases; D010446:Peptide Fragments; D000097608:UDP Xylose-Protein Xylosyltransferase